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## **Meet the editor**

Dr. Alfonso J. Rodriguez-Morales is an expert in tropical diseases, particularly in Zoonotic and Vector-Borne Diseases. His research interests over the past years have been focused on malaria, Chagas disease, leishmaniasis, dengue, Zika and chikungunya, coordinating the Colombian Collaborative Network on Zika (RECOLZIKA). He is President of the Travel Medicine Committee of the

Pan American Infectious Diseases Association (API), as well as Secretary of the Colombian Infectious Diseases Association (ACIN). Since 2014 he has been recognized as Senior Researcher by the national agency of Sicence in Colombia, Colciencias. He is Professor and Appointed Director of Research of the Faculty of Health Sciences of the Universidad Tecnológica de Pereira in Pereira, Risaralda, Colombia. His H index is currently 17.

## Contents

#### **Preface XI**

#### **Section 2 Entomology 121**

## Preface

**Section 2 Entomology 121**

**VI** Contents

Chapter 7 **Vector Control in Chikungunya and Other Arboviruses 123**

Chapter 8 **Utilization of Fruit Peel Wastes for the Management of Chikungunya Vector, Aedes aegypti 133**

Sengodan Karthi and Muthugounder Subramaniam Shivakumar

Sarita Kumar, Monika Mishra, Aarti Sharma and Radhika Warikoo

Chikungunya has become an important cause of morbidity, although with a low mortality in certain areas of the world - the tropical (mainly due to vector-borne transmission) and non-tropical areas (due to sporadic vector-borne transmission and mother-to-child transmis‐ sion) - occurring in rural and urban settings (1-3). Just in Colombia, during 2014–2015, more than 3 million cases were estimated to have occurred, including severe and atypical cases as well as deaths, including pregnant and newborn cases with congenital disease (4-6). In addi‐ tion to acute disease and subacute and chronic manifestations, today known as post-chikun‐ gunya chronic inflammatory rheumatism (pCHIK-CIR) is an important condition which compromises half of the patients who have suffered this arboviral disease mainly in La Re‐ unión, France, India, and Colombia (3, 7-9). For all these reasons, research on this arboviral disease is of utmost relevance particularly in endemic settings, mostly in developing coun‐ tries, and particularly in Latin America. However, exposure to the virus in these areas in the context of globalization also gains importance given the increasing number of imported cas‐ es (10-13), even with the risk of autochthonous transmission as have occurred in the Medi‐ terranean areas of Europe, such as in South France, Eastern Spain, or Northwestern Italy (14). As with other neglected arboviruses, chikungunya deserves more research and multi‐ ple new approaches for its study. More approaches with the vision of "One Health" are clearly necessary (15). Also, more interaction between medical doctors and doctors of veteri‐ nary medicine, as the role of animal reservoirs in chikungunya, is still, by far, unknown. Holistic control approach requires both of them involved, especially because most of the burden related to chikungunya and other neglected arboviral diseases (Mayaro, Usutu, Kya‐ sanur, Oropouche, among others), would be avoidable (16). Now, there is the emergence of Zika, which can even lead to deaths, too (17-21).

With these conceptions in mind, this book includes different topics with regard to epidemi‐ ology, biology, clinical manifestations, treatment, and prevention, including entomological aspects of the wide spectrum of manifestations caused by the chikungunya virus infection, trying to update the most significant research in many of them as well as to offer a multina‐ tional perspective on different aspects. This book has been organized in two major sections: (I) "Clinical and Epidemiological Aspects" and (II) "Entomology." Section I includes topics covering epidemiological and clinical experience and studies in Colombia, Chile, Mexico, La Reunión, France, and India, including the infection during pregnancy and children, import‐ ed cases, ocular manifestations, coinfections, and therapeutics. Section II includes topics cov‐ ering entomological aspects, related to vector control, and new options for biological control of *Aedes aegypti,* the main vector of chikungunya.

Commissioning of this book has been related in part to my recent involvement in chikungu‐ nya research, making the first publications of Colombia, as well as among the first in Latin

America about multiple aspects of this arboviral disease. Part of this is a clear reflection of the work impulse at the Research Group Infection Public Health and Infection of the Faculty of Health Sciences of Universidad Tecnológica de Pereira, directed by Dr. Guillermo Javier Lagos-Grisales, not just a partner and a colleague, but mainly a friend and an extreme be‐ liever in our work.

Following the same philosophy that we had on my three previous books with InTech, *Cur‐ rent Topics in Tropical Medicine* (22), *Current Topics in Public Health* (23), and *Current Topics in Echinococcosis* (24), this book does not intend to be an exhaustive compilation, and this first edition has included not just multiple different topics but also a wide geographical partici‐ pation from many countries of different regions of the world. Its online availability through the website of InTech, as well as the possibility to upload the complete book or their chap‐ ters in personal websites and institution repositories, allows it to reach a wide audience.

I would like to give a very especial thanks to InTech (for the fourth time), and particularly to Iva Simcic (Publishing Process Manager), for the opportunity to edit this interesting and im‐ portant book, as well as for their constant support.

I want to take the appropriate time and space, as I used to do, to dedicate this book to my beloved family (Aurora, Alfonso José, Alejandro, and Andrea, the neurologist) and particu‐ larly to my lovely wife, Diana. After 5 years together, I am so certain she is everything to me.  And due to her support, projects like this one would be not only just possible, but also successful. She is the highest blessing in my life, my soul mate, and my strongest support for any journey; she provides everything in my life, day to day. Also I would like to thank my friends and my undergraduate and postgraduate students of health sciences in Colombia, Venezuela, and around Latin America. It is time to say thanks to my colleagues at the Working Group on Zoonoses, the International Society for Chemo‐ therapy, and the Committee on Zoonoses and Haemorrhagic Fevers of the Colombian Infec‐ tious Diseases Society (ACIN), and to more than 40 members of our Colombian Collaborative Network on Zika (RECOLZIKA) (www.RECOLZIKA.org), which I have the pleasure to chair, especially to my friends Wilmer E. Villamil-Gómez, Alberto Paniz-Mon‐ dolfi, and Jorge L. Alvarado-Socarras, among many others across Colombia and Latin Amer‐ ica. I would like to thank Dr. Juliana Buitrago-Jaramillo, the former Dean of the Faculty of Health Sciences, Universidad Tecnológica de Pereira, who supported most of the efforts of our research group, Public Health and Infection. Special thanks to my friend and colleague Dr. Guillermo J. Lagos-Grisales, MD, MPH. Also I would like to thank the current Dean, Dr. Rodolfo Cabrales, who has been an enthusiast and supporter of our research activity. Mem‐ bers of our research group and incubator consist of young and enthusiastic medical students and some veterinary medical students, as well as young medical doctors, who are pursuing significant improvements in the understanding of the epidemiology of zoonotic, vectorborne, parasitic and, in general, infectious diseases, in our country with international projec‐ tion. The year 2016 has been highly productive for this recognized group, which is positioning as a leader in infectious disease epidemiology research in the Coffee-Triangle Region and very soon in the country. One chapter was written by two of our graduates. Thanks to Dr. Mondragón, who helped in the critical review of the editor's chapter.

Finally, I hope our readers enjoy this publication as much as I did reading the chapters of *Current Topics in Chikungunya.*

#### **References**

America about multiple aspects of this arboviral disease. Part of this is a clear reflection of the work impulse at the Research Group Infection Public Health and Infection of the Faculty of Health Sciences of Universidad Tecnológica de Pereira, directed by Dr. Guillermo Javier Lagos-Grisales, not just a partner and a colleague, but mainly a friend and an extreme be‐

Following the same philosophy that we had on my three previous books with InTech, *Cur‐ rent Topics in Tropical Medicine* (22), *Current Topics in Public Health* (23), and *Current Topics in Echinococcosis* (24), this book does not intend to be an exhaustive compilation, and this first edition has included not just multiple different topics but also a wide geographical partici‐ pation from many countries of different regions of the world. Its online availability through the website of InTech, as well as the possibility to upload the complete book or their chap‐ ters in personal websites and institution repositories, allows it to reach a wide audience.

I would like to give a very especial thanks to InTech (for the fourth time), and particularly to Iva Simcic (Publishing Process Manager), for the opportunity to edit this interesting and im‐

I want to take the appropriate time and space, as I used to do, to dedicate this book to my beloved family (Aurora, Alfonso José, Alejandro, and Andrea, the neurologist) and particu‐ larly to my lovely wife, Diana. After 5 years together, I am so certain she is everything to me.  And due to her support, projects like this one would be not only just possible, but also successful. She is the highest blessing in my life, my soul mate, and my strongest support for any journey; she provides everything in my life, day to day. Also I would like to thank my friends and my undergraduate and postgraduate students of health sciences in Colombia, Venezuela, and around Latin America. It is time to say thanks to my colleagues at the Working Group on Zoonoses, the International Society for Chemo‐ therapy, and the Committee on Zoonoses and Haemorrhagic Fevers of the Colombian Infec‐ tious Diseases Society (ACIN), and to more than 40 members of our Colombian Collaborative Network on Zika (RECOLZIKA) (www.RECOLZIKA.org), which I have the pleasure to chair, especially to my friends Wilmer E. Villamil-Gómez, Alberto Paniz-Mon‐ dolfi, and Jorge L. Alvarado-Socarras, among many others across Colombia and Latin Amer‐ ica. I would like to thank Dr. Juliana Buitrago-Jaramillo, the former Dean of the Faculty of Health Sciences, Universidad Tecnológica de Pereira, who supported most of the efforts of our research group, Public Health and Infection. Special thanks to my friend and colleague Dr. Guillermo J. Lagos-Grisales, MD, MPH. Also I would like to thank the current Dean, Dr. Rodolfo Cabrales, who has been an enthusiast and supporter of our research activity. Mem‐ bers of our research group and incubator consist of young and enthusiastic medical students and some veterinary medical students, as well as young medical doctors, who are pursuing significant improvements in the understanding of the epidemiology of zoonotic, vectorborne, parasitic and, in general, infectious diseases, in our country with international projec‐ tion. The year 2016 has been highly productive for this recognized group, which is positioning as a leader in infectious disease epidemiology research in the Coffee-Triangle Region and very soon in the country. One chapter was written by two of our graduates.

Thanks to Dr. Mondragón, who helped in the critical review of the editor's chapter.

Finally, I hope our readers enjoy this publication as much as I did reading the chapters of

portant book, as well as for their constant support.

*Current Topics in Chikungunya.*

liever in our work.

VIII Preface

[1] Alfaro-Toloza P, Clouet-Huerta DE, Rodriguez-Morales AJ; Chikungunya, the emerging migratory rheumatism. Lancet Infect Dis 2015;15(5):510-2. doi: 10.1016/S1473-3099(15)70160-X.

[2] Hidalgo-Zambrano DM, Jiménez-Canizales CE, Alzate-Piedrahita JA, et al.; Electrocar‐ diographic changes in patients with chikungunya fever. Revista Panamericana de Infectolo‐ gía 2015;17(3).

[3] Rodriguez-Morales AJ, Cardona-Ospina JA, Villamil-Gomez W, et al.; How many pa‐ tients with post-chikungunya chronic inflammatory rheumatism can we expect in the new endemic areas of Latin America? Rheumatol Int 2015;35(12):2091-4. doi: 10.1007/ s00296-015-3302-5.

[4] Cardona-Ospina JA, Henao-SanMartin V, Paniz-Mondolfi AE, et al.; Mortality and fatali‐ ty due to Chikungunya virus infection in Colombia. J Clin Virol 2015;70:14-5. doi: 10.1016/ j.jcv.2015.07.001.

[5] Hoz JM, Bayona B, Viloria S, et al.; Fatal cases of Chikungunya virus infection in Colom‐ bia: Diagnostic and treatment challenges. J Clin Virol 2015;69:27-9. doi: 10.1016/j.jcv. 2015.05.021.

[6] Villamil-Gomez W, Alba-Silvera L, Menco-Ramos A, et al.; Congenital Chikungunya Vi‐ rus Infection in Sincelejo, Colombia: A Case Series. J Trop Pediatr 2015;61(5):386-92. doi: 10.1093/tropej/fmv051.

[7] Cardona-Ospina JA, Vera-Polania F, Rodriguez-Morales AJ; Chikungunya or not, differ‐ ential diagnosis and the importance of laboratory confirmation for clinical and epidemiolog‐ ical research: comment on the article by Rosario et al. Clin Rheumatol 2016;35(3):829-30. doi: 10.1007/s10067-015-2995-x.

[8] Rodriguez-Morales AJ, Gil-Restrepo AF, Ramirez-Jaramillo V, et al.; Post-chikungunya chronic inflammatory rheumatism: results from a retrospective follow-up study of 283 adult and child cases in La Virginia, Risaralda, Colombia. F1000Res 2016;5:360. doi: 10.12688/ f1000research.8235.2.

[9] Cardona-Ospina JA, Diaz-Quijano FA, Rodriguez-Morales AJ; Burden of chikungunya in Latin American countries: estimates of disability-adjusted life-years (DALY) lost in the 2014 epidemic. Int J Infect Dis 2015;38:60-1. doi: 10.1016/j.ijid.2015.07.015.

[10] Rodriguez-Morales AJ, Bedoya-Arias JE, Ramirez-Jaramillo V, et al.; Using geographic information system (GIS) to mapping and assess changes in transmission patterns of chikun‐ gunya fever in municipalities of the Coffee-Triangle region of Colombia during 2014-2015 outbreak: Implications for travel advice. Travel Med Infect Dis 2016;14(1):62-5. doi: 10.1016/ j.tmaid.2015.06.009.

[11] Rodriguez-Morales AJ, Cardenas-Giraldo EV, Montoya-Arias CP, et al.; Mapping chi‐ kungunya fever in municipalities of one coastal department of Colombia (Sucre) using geo‐ graphic information system (GIS) during 2014 outbreak: Implications for travel advice. Travel Med Infect Dis 2015;13(3):256-8. doi: 10.1016/j.tmaid.2015.05.007.

[12] Rodriguez-Morales AJ, Villamil-Gomez WE, Franco-Paredes C; The arboviral burden of disease caused by co-circulation and co-infection of dengue, chikungunya and Zika in the Americas. Travel Med Infect Dis 2016;14(3):177-9. doi: 10.1016/j.tmaid.2016.05.004.

[13] Jimenez-Canizales CE, Medina-Gaitan DA, Mondragon-Cardona AE, et al.; From im‐ ported to an endemic disease: impact of Chikungunya virus disease in the hospital epidemi‐ ology, Tolima, Colombia, 2014-2015. Recent Pat Antiinfect Drug Discov 2015;10(1):64-6.

[14] Noel H, Rizzo C; Spread of chikungunya from the Caribbean to mainland Central and South America: a greater risk of spillover in Europe? Euro Surveill 2014;19(28):20855.

[15] Rodriguez-Morales AJ, Schlagenhauf P; Zoonoses and travel medicine: "one world--one health". Travel Med Infect Dis 2014;12(6 Pt A):555-6. doi: 10.1016/j.tmaid.2014.11.003.

[16] Patino-Barbosa AM, Bedoya-Arias JE, Cardona-Ospina JA, et al.; Bibliometric assess‐ ment of the scientific production of literature regarding Mayaro. J Infect Public Health 2016;9(4):532-4. doi: 10.1016/j.jiph.2015.10.001.

[17] Martinez-Pulgarin DF, Acevedo-Mendoza WF, Cardona-Ospina JA, et al.; A bibliomet‐ ric analysis of global Zika research. Travel Med Infect Dis 2016;14(1):55-7. doi: 10.1016/ j.tmaid.2015.07.005.

[18] Rodriguez-Morales AJ; Dengue and chikungunya were not enough: Now also Zika ar‐ rived. Archivos de Medicina 2015;11(2). doi: 10.3823/1245.

[19] Arzuza-Ortega L, Polo A, Perez-Tatis G, et al.; Fatal Sickle Cell Disease and Zika Virus Infection in Girl from Colombia. Emerg Infect Dis 2016;22(5):925-7. doi: 10.3201/ eid2205.151934.

[20] Rodriguez-Morales AJ; Zika: the new arbovirus threat for Latin America. J Infect Dev Ctries 2015;9(6):684-5. doi: 10.3855/jidc.7230.

[21] Sarmiento-Ospina A, Vasquez-Serna H, Jimenez-Canizales CE, et al.; Zika virus associ‐ ated deaths in Colombia. Lancet Infect Dis 2016. doi: 10.1016/S1473-3099(16)30006-8.

[22] Rodriguez-Morales AJ. (Editor). Current Topics in Tropical Medicine. ISBN 978-953-51-0274-8. InTech, Croatia, March 2012.

[23] Rodriguez-Morales AJ. (Editor). Current Topics in Public Health. ISBN 978-953-51-1121-4. InTech, Croatia, May 2013.

[24] Rodriguez-Morales AJ. (Editor). Current Topics in Echinococcosis. ISBN 978-953-51-2159-6. InTech, Croatia, September 2015.

#### **Prof. Alfonso J. Rodriguez-Morales**

MD, MSc, DTM&H, FRSTMH(Lon), FFTM RCPS(Glasg), FACE, PhD(c) Part-time faculty instructor, Risk Factors (Epidemiology) (Coordinator) Department of Community Medicine, School of Medicine Lecturer, Frontiers Research, School of Veterinary Medicine and Zootechnics Faculty of Health Sciences, Universidad Tecnológica de Pereira, Pereira, Risaralda, Colombia Lecturer, Postgraduate in Epidemiology, Fundación Universitaria del Área Andina Seccional Pereira, Pereira, Risaralda, Colombia Cochairman, Working Group on Zoonoses, International Society for Chemotherapy (ISC) Secretary, Colombian Association of Infectious Diseases (ACIN) Member of the Committee on Zoonoses and Hemorrhagic Fevers, ACIN President, ACIN Chapter Coffee-Triangle Region President, Committee on Travel Medicine Pan American Association of Infectious Diseases Senior Researcher, Colciencias (2015–2019) **Clinical and Epidemiological Aspects**

[14] Noel H, Rizzo C; Spread of chikungunya from the Caribbean to mainland Central and

[15] Rodriguez-Morales AJ, Schlagenhauf P; Zoonoses and travel medicine: "one world--one

[16] Patino-Barbosa AM, Bedoya-Arias JE, Cardona-Ospina JA, et al.; Bibliometric assess‐ ment of the scientific production of literature regarding Mayaro. J Infect Public Health

[17] Martinez-Pulgarin DF, Acevedo-Mendoza WF, Cardona-Ospina JA, et al.; A bibliomet‐ ric analysis of global Zika research. Travel Med Infect Dis 2016;14(1):55-7. doi: 10.1016/

[18] Rodriguez-Morales AJ; Dengue and chikungunya were not enough: Now also Zika ar‐

[19] Arzuza-Ortega L, Polo A, Perez-Tatis G, et al.; Fatal Sickle Cell Disease and Zika Virus Infection in Girl from Colombia. Emerg Infect Dis 2016;22(5):925-7. doi: 10.3201/

[20] Rodriguez-Morales AJ; Zika: the new arbovirus threat for Latin America. J Infect Dev

[21] Sarmiento-Ospina A, Vasquez-Serna H, Jimenez-Canizales CE, et al.; Zika virus associ‐

[22] Rodriguez-Morales AJ. (Editor). Current Topics in Tropical Medicine. ISBN

[23] Rodriguez-Morales AJ. (Editor). Current Topics in Public Health. ISBN

[24] Rodriguez-Morales AJ. (Editor). Current Topics in Echinococcosis. ISBN

Faculty of Health Sciences, Universidad Tecnológica de Pereira, Pereira, Risaralda, Colombia

Cochairman, Working Group on Zoonoses, International Society for Chemotherapy (ISC)

Lecturer, Postgraduate in Epidemiology, Fundación Universitaria del Área Andina

MD, MSc, DTM&H, FRSTMH(Lon), FFTM RCPS(Glasg), FACE, PhD(c) Part-time faculty instructor, Risk Factors (Epidemiology) (Coordinator)

Lecturer, Frontiers Research, School of Veterinary Medicine and Zootechnics

Department of Community Medicine, School of Medicine

Secretary, Colombian Association of Infectious Diseases (ACIN)

Member of the Committee on Zoonoses and Hemorrhagic Fevers, ACIN

Seccional Pereira, Pereira, Risaralda, Colombia

President, ACIN Chapter Coffee-Triangle Region

President, Committee on Travel Medicine Pan American Association of Infectious Diseases Senior Researcher, Colciencias (2015–2019)

**Prof. Alfonso J. Rodriguez-Morales**

ated deaths in Colombia. Lancet Infect Dis 2016. doi: 10.1016/S1473-3099(16)30006-8.

South America: a greater risk of spillover in Europe? Euro Surveill 2014;19(28):20855.

health". Travel Med Infect Dis 2014;12(6 Pt A):555-6. doi: 10.1016/j.tmaid.2014.11.003.

2016;9(4):532-4. doi: 10.1016/j.jiph.2015.10.001.

Ctries 2015;9(6):684-5. doi: 10.3855/jidc.7230.

978-953-51-0274-8. InTech, Croatia, March 2012.

978-953-51-1121-4. InTech, Croatia, May 2013.

978-953-51-2159-6. InTech, Croatia, September 2015.

rived. Archivos de Medicina 2015;11(2). doi: 10.3823/1245.

j.tmaid.2015.07.005.

X Preface

eid2205.151934.

## **Chikungunya, a Global Threat Currently Circulating in Latin America**

Alfonso J. Rodriguez-Morales, Jaime Andrés Cardona-Ospina and Wilmer E. Villamil-Gómez

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/64808

#### **Abstract**

Chikungunya fever (CHIK) is a highly important arbovirosis currently established in Lat‐ in America and the Caribbean (LAC); its acute and chronic burden is an overlooked issue for policy makers. Disease spread control and proper management of chronic-derived se‐ quelae do not seem like a realistic goal in short- and mid-term. The CHIKV circulating in the Western Hemisphere is closely related to strains from Philippines, China, and Yap (Federated States of Micronesia), and vertical and horizontal transmission of infection has been reported. Pathogenesis is still not well understood, and vaccines are under develop‐ ment yet. Here, we provide a summary of information regarding LAC spread of the dis‐ ease from a public health, clinical and molecular perspective, particularly from the experience in Colombia.

**Keywords:** Chikungunya, Latin America, public health, molecular epidemiology, clinical manifestations

#### **1. Introduction**

Chikungunya fever (CHIK) is a highly important arbovirosis to Latin America and the Caribbean (LAC) because it is an infectious disease that have evolved from a simple threat to an established disease with acute and chronic burden to almost all the American continent, both mainland and overseas territories. Moreover, the presence of suitable ecological condi‐ tions in nontropical areas and our highly interconnected world have led to the report of cases in at least four continents in the world. CHIK is an arthritogenic fever that has arrived to stay in the Americas. After its introduction in 2013 to the island of Saint-Marteen (two autochtho‐ nous cases confirmed on December 6, 2013), it quickly spread through overseas Caribbean

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

territories with autochthonous transmission (Martinique and Saint Marteen, December 19, 2013; Guadeloupe, December 24, 2013; Saint Berthelemy, December 31, 2013; and British Virgin Islands, January 15, 2014). Next, on February 21, the World Health Organization (WHO) confirmed the arriving of CHIK to mainland South America in French Guiana with seven confirmed cases (two autochthonous). Since then, the disease has spread over the entire continent. Until today, it continues accounting for important acute and chronic burden to the healthcare systems of the region [1–7]. For example, in Colombia, until June 2016, more than 16,000 new cases of CHIK have been reported.

Currently, almost every country in LAC has reported autochthonous transmission of CHIK, some of them in confined territories, but others such as Colombia, Venezuela, and Ecuador with a more generalized and intense disease transmission. Non-LAC territories have suffered the impact of travel and suitable ecological conditions with vector availability (*Aedes aegypti and Aedes albopictus)*. The United States of America presently report mainland autochthonous disease transmission in Florida, and in Europe the vector is widely spread through Italy, the southern coast of Spain and France, and some areas of Switzerland, Croatia, Montenegro, Slovenia, Albania, Greece, and Romania [8]. Additionally, although previous CHIK cases have been reported in Europe, alongside the LAC outbreak, there were mainland reported cases in France and Spain in 2014 and 2015, respectively. On October 21, 2014, the National IHR Focal Point for France notified the WHO of four laboratory confirmed and locally acquired CHIK cases in Montpellier. The four cases occurred within a same family who did not have any history of traveling outside France or their district of residence, but who lived near to an imported case from Cameroon. This was the first time that locally acquired transmission of CHIK has been detected in France since 2010 [9]. On the other hand, on August 3, 2015, the WHO was notified by the National IHR Focal Point for Spain of a case of CHIK in the city of Gandia, Valencian Community. The patient, a 60-year-old man, had no history of travel outside the European Region. A regional laboratory identified him with the detection by ELISA of IgM titers and subsequent IgG seroconversion. However, the National Reference Laboratory failed to confirm these results and it apparently was a false positive [10]. Likewise on September 9, 2015, the Ministry of Health and Social Affairs of Senegal notified the WHO of the beginning of active circulation of chikungunya virus (CHIKV) on August 27 in the region of Kédougou, where the latest active circulation was reported between 2009 and 2010 [11].

As showed, CHIKV can easily be spread into areas where suitable ecological conditions are done. In 2016, 16,653 CHIK cases in LAC have been newly diagnosed, both suspected and confirmed (epidemiological week 7) [12]. By the same time, in 2014, there were 1980 cases, but the current data are only about 17% of the reported cases in the same epidemiological week in 2015. Although it is possible that CHIK cases this year would be importantly lower than the previous, attention must be paid because probably it is going to have an epidemiological behavior that resembles dengue with episodes of seasonal epidemic outbreaks. Moreover, after the arriving of Zika to the region, efforts must be oriented not only to vector control programs but to develop proper diagnosis, treatment, and follow-up strategies in order to grant man‐ agement and assessment of acute and chronic symptoms. Chikungunya, dengue, and Zika are three arbovirosis that already pose an important burden to LAC healthcare systems. They have showed our weaknesses in managing infectious disease spread and taught us that viral emerging infectious diseases are more than febrile illnesses. The latent threat of introduction of other *Aedes* sp. transmitted arbovirosis, like Mayaro or other viral hemorrhagic fevers transmitted for arthropods, call our attention to learn lesson and to take planed actions.

#### **2. Virology and molecular epidemiology**

territories with autochthonous transmission (Martinique and Saint Marteen, December 19, 2013; Guadeloupe, December 24, 2013; Saint Berthelemy, December 31, 2013; and British Virgin Islands, January 15, 2014). Next, on February 21, the World Health Organization (WHO) confirmed the arriving of CHIK to mainland South America in French Guiana with seven confirmed cases (two autochthonous). Since then, the disease has spread over the entire continent. Until today, it continues accounting for important acute and chronic burden to the healthcare systems of the region [1–7]. For example, in Colombia, until June 2016, more than

Currently, almost every country in LAC has reported autochthonous transmission of CHIK, some of them in confined territories, but others such as Colombia, Venezuela, and Ecuador with a more generalized and intense disease transmission. Non-LAC territories have suffered the impact of travel and suitable ecological conditions with vector availability (*Aedes aegypti and Aedes albopictus)*. The United States of America presently report mainland autochthonous disease transmission in Florida, and in Europe the vector is widely spread through Italy, the southern coast of Spain and France, and some areas of Switzerland, Croatia, Montenegro, Slovenia, Albania, Greece, and Romania [8]. Additionally, although previous CHIK cases have been reported in Europe, alongside the LAC outbreak, there were mainland reported cases in France and Spain in 2014 and 2015, respectively. On October 21, 2014, the National IHR Focal Point for France notified the WHO of four laboratory confirmed and locally acquired CHIK cases in Montpellier. The four cases occurred within a same family who did not have any history of traveling outside France or their district of residence, but who lived near to an imported case from Cameroon. This was the first time that locally acquired transmission of CHIK has been detected in France since 2010 [9]. On the other hand, on August 3, 2015, the WHO was notified by the National IHR Focal Point for Spain of a case of CHIK in the city of Gandia, Valencian Community. The patient, a 60-year-old man, had no history of travel outside the European Region. A regional laboratory identified him with the detection by ELISA of IgM titers and subsequent IgG seroconversion. However, the National Reference Laboratory failed to confirm these results and it apparently was a false positive [10]. Likewise on September 9, 2015, the Ministry of Health and Social Affairs of Senegal notified the WHO of the beginning of active circulation of chikungunya virus (CHIKV) on August 27 in the region of Kédougou,

where the latest active circulation was reported between 2009 and 2010 [11].

As showed, CHIKV can easily be spread into areas where suitable ecological conditions are done. In 2016, 16,653 CHIK cases in LAC have been newly diagnosed, both suspected and confirmed (epidemiological week 7) [12]. By the same time, in 2014, there were 1980 cases, but the current data are only about 17% of the reported cases in the same epidemiological week in 2015. Although it is possible that CHIK cases this year would be importantly lower than the previous, attention must be paid because probably it is going to have an epidemiological behavior that resembles dengue with episodes of seasonal epidemic outbreaks. Moreover, after the arriving of Zika to the region, efforts must be oriented not only to vector control programs but to develop proper diagnosis, treatment, and follow-up strategies in order to grant man‐ agement and assessment of acute and chronic symptoms. Chikungunya, dengue, and Zika are

16,000 new cases of CHIK have been reported.

4 Current Topics in Chikungunya

CHIKV is a member of the genus *Alphavirus,* family *Togaviridae*, that was first isolated from the serum of a febrile human in Tanganyika (Tanzania) in 1952–1953 [13,14]. However, reported cases from India and Japan have suggested that CHIKV epidemics could have occurred as early as 1779 [15]. Besides, after its isolation, the virus was found repeatedly in numerous countries in Central, Southern, and Western Africa, as well as in many areas of Asia, and it has caused multiple outbreaks and epidemics in Africa, Southeast Asia, and Southern Europe [16–18].

The CHIKV is an enveloped, spherical virus with a diameter of 60–70 nm. It has a RNA, positive sense, linear genome of 11.8 kb that resembles eukaryotic mRNAs; given that at the 5′ end, it has a methyl guanylate cap, which is a nonstructural poly-protein precursor, and at the 3′ end, it has a poly(A) tail [17]. The 5′ precursor is cleaved into nsP1, nsP2, nsP3, and nsP4, which are involved in the virus replication and have functions and structures that are shared by other alphaviruses [17,19–21]. The nsP1 protein functions as cytoplasmic RNA capping enzyme, the nsP2 protein is a cysteine protease with a partially constricted substrate-binding site and two separate domains with helicase and protease activity [20], the nsP3 protein is essential for negative strand RNA synthesis, and the nsP4 protein works as an RNA-dependent RNA polymerase [17–19,21]. The 3′ poly(A) tail consists of 26S mRNA whose products include the structural proteins: the surface glycoproteins (E1 and E2), the capsid protein, and small peptides (E3 and 6K). The surface glycoprotein E2 has a role in viral attachment, and the surface glycoprotein E1 is the fusion protein that facilitates the viral entry [18,19,22].

Currently, there are three CHIKV-identified genotypes based on the E1 gene and the full genome sequence: East/Central/South African (ECSA), West African, and Asian. Phylogenetic analyses suggest that CHIKV spread from Africa to Asia episodically [23,24] and that the CHIKV strains circulating in the Caribbean came from the >2005 Southeast Asian clade, which previously moved into Western and South Pacific (American Samoa and Yap) and then to the Western Hemisphere. The CHIKV circulating in the Western Hemisphere is closely related to strains from Philippines, China, and Yap (Federated States of Micronesia) [25–30]. By contrast, the circulation of the ECSA genotype has been confirmed in Brazil apparently imported from Angola [31]. During the current LAC epidemics, the virus has showed mutation rates that are in accordance with previous evolutionary rate model, which predicted approximately 10 nucleotide mutations over the entire genome during the course of a 1-year epidemic [23,26,30]. The LAC CHIKV possess two unique amino acid differences and a 12-nucleotide deletion that could be useful in future for tracking of this strain [26].

#### **3. Pathogenesis and disease transmission**

Conventionally, CHIKV transmission is considered to be through flying arthropods of the *A. aegypti* o *A. albopictus* species. However, evidence suggested that viable infective virus is excreted in the saliva of monkeys, mice, and humans, and it could be a source of infection particularly in immunocompromised patients [32,33]. Vertical transmission has also been reported [34,35]. Despite some studies failed to show effect of CHKV infection during pregnancy on major obstetrical outcomes or congenital anomalies, long-term follow-up studies have reported poor neurocognitive outcomes of newborns and even poorer results in patients with neonatal CHIKV encephalopathy [36,37].

After its entry to the human host, the CHIKV first replicates in the skin fibroblasts [38,39], next it enters to the circulatory system, and triggers an early type I interferon response [40]. Apparently, alterations in this response are associated with more severe disease and death [41]. Next, it disseminates from blood to various tissues, it lodges in immune-privileged niches, and it replicates in the joints and skeletal muscles that are associated with extensive inflammatory cell recruitment [38,40,42–45]. CHIKV infection can persist in mononuclear cells and macro‐ phages that are another primary cellular target and help in virus dissemination and chronic articular symptoms [38,46,47]. It has been proposed that viral persistence is associated with expression of interferon (IFN)-α, interleukin (IL)-10, and monocyte chemotactic protein 1 (MCP-1 or CCL2) [40]. Chikungunya infection causes high levels of IFN-α, suggesting strong innate immunity, along with the production of IL-4, IL-10, and IFN-γ, suggesting the engage‐ ment of the adaptive immunity. Notably, circulating T lymphocytes showed a CD8+ T lymphocyte response in the early stages of the disease and a CD4+ T lymphocyte-mediated response in the later stages, and IFN-γ and IL-12 levels have been observed to rise dramatically during the acute phase of chikungunya fever. The level of IL-12 returns to normalcy in patients who recover. In contrast, patients who develop chronic arthritis show persistently high IL-12 levels. Histologic examination of synovia from patients with chronic arthritis following chikungunya fever has revealed joint inflammation due to macrophages containing viral material. Elevated expression of MCP-1, MCP-2, and MCP-3 has been associated with bone reabsorption and bone lose, and CHIKV seems to favor a pro-osteoclastic microenvironment disrupting the receptor activator of nuclear factor-κB ligand/osteoprotegerin (RANKL/OPG) ratio [43,48].

Support cells of the central nervous system, such as astrocytes and oligodendrocytes, have shown to be infected with CHIKV in human, primate, and mice models [49,50]. Apparently, the astrocytes play an important role in replicating the virus and are susceptible to die because of the infection, whereas the microglia seems to be infection-resistant [50]. The infected cells are induced to express high levels of cytokines and chemokines related to an upregulation on innate immune response [50,51]. The adaptive immune response apparently occurs early in the infection. Higher and early increase of IgG3 titers has been correlated with efficient viral clearance and long-term viral protection [52], whereas higher level of C-reactive protein is related to lymphopenia, lower monocyte level, neutrophilia, and high viral load [19,53].

#### **4. Clinical manifestations and chronic sequelae**

**3. Pathogenesis and disease transmission**

6 Current Topics in Chikungunya

with neonatal CHIKV encephalopathy [36,37].

ratio [43,48].

Conventionally, CHIKV transmission is considered to be through flying arthropods of the *A. aegypti* o *A. albopictus* species. However, evidence suggested that viable infective virus is excreted in the saliva of monkeys, mice, and humans, and it could be a source of infection particularly in immunocompromised patients [32,33]. Vertical transmission has also been reported [34,35]. Despite some studies failed to show effect of CHKV infection during pregnancy on major obstetrical outcomes or congenital anomalies, long-term follow-up studies have reported poor neurocognitive outcomes of newborns and even poorer results in patients

After its entry to the human host, the CHIKV first replicates in the skin fibroblasts [38,39], next it enters to the circulatory system, and triggers an early type I interferon response [40]. Apparently, alterations in this response are associated with more severe disease and death [41]. Next, it disseminates from blood to various tissues, it lodges in immune-privileged niches, and it replicates in the joints and skeletal muscles that are associated with extensive inflammatory cell recruitment [38,40,42–45]. CHIKV infection can persist in mononuclear cells and macro‐ phages that are another primary cellular target and help in virus dissemination and chronic articular symptoms [38,46,47]. It has been proposed that viral persistence is associated with expression of interferon (IFN)-α, interleukin (IL)-10, and monocyte chemotactic protein 1 (MCP-1 or CCL2) [40]. Chikungunya infection causes high levels of IFN-α, suggesting strong innate immunity, along with the production of IL-4, IL-10, and IFN-γ, suggesting the engage‐ ment of the adaptive immunity. Notably, circulating T lymphocytes showed a CD8+ T lymphocyte response in the early stages of the disease and a CD4+ T lymphocyte-mediated response in the later stages, and IFN-γ and IL-12 levels have been observed to rise dramatically during the acute phase of chikungunya fever. The level of IL-12 returns to normalcy in patients who recover. In contrast, patients who develop chronic arthritis show persistently high IL-12 levels. Histologic examination of synovia from patients with chronic arthritis following chikungunya fever has revealed joint inflammation due to macrophages containing viral material. Elevated expression of MCP-1, MCP-2, and MCP-3 has been associated with bone reabsorption and bone lose, and CHIKV seems to favor a pro-osteoclastic microenvironment disrupting the receptor activator of nuclear factor-κB ligand/osteoprotegerin (RANKL/OPG)

Support cells of the central nervous system, such as astrocytes and oligodendrocytes, have shown to be infected with CHIKV in human, primate, and mice models [49,50]. Apparently, the astrocytes play an important role in replicating the virus and are susceptible to die because of the infection, whereas the microglia seems to be infection-resistant [50]. The infected cells are induced to express high levels of cytokines and chemokines related to an upregulation on innate immune response [50,51]. The adaptive immune response apparently occurs early in the infection. Higher and early increase of IgG3 titers has been correlated with efficient viral clearance and long-term viral protection [52], whereas higher level of C-reactive protein is related to lymphopenia, lower monocyte level, neutrophilia, and high viral load [19,53].

It was previously believed that asymptomatic seroconversion was a rare event. However, results point that the subclinical: symptomatic proportion is at least of 4.6:1 patients [54]. The clinical course of CHIK could be divided into three phases: acute, subacute, and chronic. The acute phase has usually been considered from the start of the symptoms (day 0) until the day 10. The most frequent symptoms are arthralgia, fever, and rash [28,55,56]. Other symptoms that could be present are headache, myalgia, pruritus, dizziness, nausea, vomiting, diarrhea, asthenia, red eyes, and although unusual, hemorrhagic symptoms could be present too [28]. The arthralgia usually is a bilateral and symmetric polyarthralgia of large joints that involves the appendicular skeleton; it is more severe in viremic patients, and the joints more frequently affected are of the lower limbs particularly, knees and ankles. Impairment of the finger joints is more frequent in women like the periarticular swelling too. Some patients can feel pain in previous bone fractures or ligament injuries as well as pain along ligament insertions and talalgia [57,58]. Likewise, skin involvement is important, although some studies reporting cutaneous manifestations are limited by the lack of confirmation of infection through serolog‐ ical test. Dermatological lesions comprise a wide spectrum. It could be morbilliform eruption, the most common type of lesion, scaling, confluent macular erythema, intertrigo, hypermela‐ nosis, xerosis, excoriated papules, urticaria, petechial spots, and bullae, among others [58,59]. The macular erythematous rash could appear at fourth day of fever, while dengue rash appears between days 5 and 6, and in Zika fever it could appear on the first symptomatic day. Mucosal involvement has been reported, with aphthous ulcers in mouth, conjunctival injection, and nasal ulceration with nasal skin necrosis [60,61]. Similarly, CHIK cases could manifest with vasculitis in legs or nose with complications that could lead to amputation. Laboratory findings are often unremarkable; lymphopenia and thrombocytopenia could be present but are rare and slight elevation of hepatic aminotransferases could be observed [58]. During this time, there is a lot of overlap between symptoms caused by CHIK, dengue, and Zika, and for this reason differential diagnosis must be made through specific laboratory assessment (Specific IgM titers or RT-PCR) [62,63]. However, some features could help to guide clinical probability in field work. For instance, acute reactants such as C-reactive protein and sedimentation rate could be high, in contrast with dengue and Zika [64–103]. Cardiovascular assessment through electrocardiographic and echocardiographic imaging must be strongly considered. Ventricu‐ lar and supraventricular arrhythmias and signs of myocarditis or acute effusive pericarditis could be present [104].

During the acute phase of the disease, some patients evolve to some clinical presentations that, because it is apparent rare occurrence, have been called "atypical manifestations" that include severe disease manifestations. These clinical manifestations include comprises in neurological, respiratory, cardiovascular, and cutaneous systems, among others that could evolve to death [3,61,64–68]. Older age and comorbidities are associated with the appearance of severe cases, death, and evolution to chronic forms of the disease [64]. Ocular manifestations are important too, being the anterior uveitis the most frequent, although retinitis and optic neuritis have also been reported [69]. During the outbreak of 2006 in Reunion Island, mortality attributable to CHIK was recorded, and during the LAC outbreak, fatalities have been noted with an estimated case fatality rate of 0.012% [3,64,65]. It is important to highlight that co-infection could be an issue where co-circulation of CHIK, dengue, and Zika has been reported since mixed clinical pictures could be present.

After 10 days of infection, the majority of patients will improve and symptoms will disappear, but there is a proportion of patients that will evolve to the subacute and chronic phase of the disease. The chronic phase is usually defined as the presence of symptoms at least for 2 or 3 months. The symptoms present during this phase affect quality of life and they can be derived from different involving systems [70]. According with previous estimates, 41.57% of CHIKinfected people would develop chronic inflammatory rheumatism (pCHIK-CIR), both arthritis and arthralgia, at 12 months [71]. Estimates derived from a systematic review and metaanalysis [105] showed, in the most conservative scenario, about 25% of CHIK would develop pCHIK-CIR, 34% considering the most representative studies, and 14% would develop chronic arthritis. Retrospective studies from cohorts in Colombia support these findings [72,73], but prospective studies are needed in order to establish the real risk of progression in LAC since geographical variation has been reported. When pCHIK-CIR appears, it usually involves ankles, knees, shoulder, and elbow [74]. And sometimes, it can mimic seronegative rheumatoid arthritis [75–77]. Although it is unknown if pCHIK-CIR is a lifetime condition, follow-up studies have found persistence of bone erosions and articular symptoms even after 6 years [78]. The risk of articular symptoms' persistence is apparently increased with older age, severity of initial joint pain, underlying osteoarthritis, gender (i.e. women), and number of comorbidities [64,70,79–81].

Although less well documented, there are other chronic worrisome sequelae that could be derived from CHIK. For example, chronic sequelae derived from post-CHIK Guillain-Barré or post-CHIK neuropsychiatric disorders such as anxiety or depression [66,67,82,83], vision defects from ocular involvement [69], or congestive heart failure from dilated cardiomyopathy associated with myocarditis [84]. Hence, although CHIK-burden is already worrisome, derived costs, both direct and indirect, are probably underestimations of the real problem. Healthcare systems of the affected areas must be aware of the possible chronic consequences of CHIK infection and efforts for prevention of infection must be done and proper follow-up of infected patients must be granted. The real scope of the problem is still unknown and more research is needed.

#### **5. Treatment and antiviral development**

Until today, CHIKV infection during the acute phase is treated with hydration, non–antiinflammatory antipyretics (acetaminophen), and symptomatic relief through the use of antihistaminic drugs or lotions for pruritus control. When pain does not relief with usual analgesia, general measures such as alternating cycles of 10 minutes of cold and 20 minutes of warm each 8 hours could be used avoiding the prescription of corticoids or nonsteroidal antiinflammatory drugs. Currently, there are no approved antivirals to treat the infection, but research in the field has been increasing. Some antiviral molecules, which act by blocking virus proteins important for virus replication, have been reported [85]. Polymerase inhibitors, mainly nucleotide, have been tested with difficulty because the core polymerase subunit nsP4, which is shared by other alphaviruses, is inactive on its own [21,85]. However, Faviparir (6 fluoro-3-hydroxy-2-pyrazinecarbox-amide), a nucleotide RNA-base analog inhibitor, is promising because it reduces CHIKV replication, as well as in other alphaviruses, in mice [86]. Likewise, efforts have been made in order to identify pharmacophore features of protease (nsP2) inhibitors [87]. Molecular modeling has been used in the identification of novel and selective inhibitors with one of them having encouraging features [88]. Other drugs, such as ribavirin, interferon, mycophenolic acid, or arbidol, with known antiviral activity against other pathogens have been proved in CHIKV infection and could potentially be used in treatment [85,89]. Equally, other drugs without conventional antiviral activity have been proposed for treatment. For instance, chloroquine has been suggested as a drug with prophylactic and therapeutic effects apparently by impairing endosomal-mediated virus entry during early stages of virus replication [90]. Other anti-parasite agents, such as ivermectin and a benzimi‐ dazole-derived drug, have showed effects on replication at early and late stages of infection [91,92]. Doxycycline combined with ribavirin effectively inhibited CHIKV replication and attenuated its infectivity in vivo in animal models [93]. Besides, some plant-derived products, such as green tea components, flavonoids, diterpene esters, and complex plant alkaloids, have showed antiviral activity against CHIKV [85,94–96].

For the chronic phase of the disease, particularly for articular symptoms, there is little highquality evidence to guide treatment. Recommendations worldwide have suggested treating inflammatory articular symptoms in an early fashion as rheumatoid arthritis, and some disease-modifying antirheumatic drugs, such as hydroxychloroquine and methotrexate, have been proved in pCHIK-CIR appa rently with good results [77,97]. Glucosamine and chondroi‐ tin sulfate could be used to treat pain in patients with previous arthrosis, and those patients with neuropathic pain pregabalin could be prescribed. Treatment of other nonarticular pCHIK chronic sequelae have been poorly studied and reported, and there is no a clinical studied and approved drug for pCHIK-CIR risk reduction. Although studies suggest that passive immu‐ nization with monoclonal antibodies may help in CHIKV-infected patients who are at risk of severe disease or in neonates born from viremic mothers [85].

#### **6. Vaccines, disease prevention and control**

estimated case fatality rate of 0.012% [3,64,65]. It is important to highlight that co-infection could be an issue where co-circulation of CHIK, dengue, and Zika has been reported since

After 10 days of infection, the majority of patients will improve and symptoms will disappear, but there is a proportion of patients that will evolve to the subacute and chronic phase of the disease. The chronic phase is usually defined as the presence of symptoms at least for 2 or 3 months. The symptoms present during this phase affect quality of life and they can be derived from different involving systems [70]. According with previous estimates, 41.57% of CHIKinfected people would develop chronic inflammatory rheumatism (pCHIK-CIR), both arthritis and arthralgia, at 12 months [71]. Estimates derived from a systematic review and metaanalysis [105] showed, in the most conservative scenario, about 25% of CHIK would develop pCHIK-CIR, 34% considering the most representative studies, and 14% would develop chronic arthritis. Retrospective studies from cohorts in Colombia support these findings [72,73], but prospective studies are needed in order to establish the real risk of progression in LAC since geographical variation has been reported. When pCHIK-CIR appears, it usually involves ankles, knees, shoulder, and elbow [74]. And sometimes, it can mimic seronegative rheumatoid arthritis [75–77]. Although it is unknown if pCHIK-CIR is a lifetime condition, follow-up studies have found persistence of bone erosions and articular symptoms even after 6 years [78]. The risk of articular symptoms' persistence is apparently increased with older age, severity of initial joint pain, underlying osteoarthritis, gender (i.e. women), and number of comorbidities

Although less well documented, there are other chronic worrisome sequelae that could be derived from CHIK. For example, chronic sequelae derived from post-CHIK Guillain-Barré or post-CHIK neuropsychiatric disorders such as anxiety or depression [66,67,82,83], vision defects from ocular involvement [69], or congestive heart failure from dilated cardiomyopathy associated with myocarditis [84]. Hence, although CHIK-burden is already worrisome, derived costs, both direct and indirect, are probably underestimations of the real problem. Healthcare systems of the affected areas must be aware of the possible chronic consequences of CHIK infection and efforts for prevention of infection must be done and proper follow-up of infected patients must be granted. The real scope of the problem is still unknown and more

Until today, CHIKV infection during the acute phase is treated with hydration, non–antiinflammatory antipyretics (acetaminophen), and symptomatic relief through the use of antihistaminic drugs or lotions for pruritus control. When pain does not relief with usual analgesia, general measures such as alternating cycles of 10 minutes of cold and 20 minutes of warm each 8 hours could be used avoiding the prescription of corticoids or nonsteroidal antiinflammatory drugs. Currently, there are no approved antivirals to treat the infection, but research in the field has been increasing. Some antiviral molecules, which act by blocking virus

mixed clinical pictures could be present.

8 Current Topics in Chikungunya

[64,70,79–81].

research is needed.

**5. Treatment and antiviral development**

Although efforts have increased up to this moment, there is no an approved vaccine for CHIK prevention. There are several vaccine strategies proven in CHIK that comprises live attenuated virus, chimeric virus, DNA vaccines, viral vector vaccines, viral subunits, inactivated virus, and virus-like particles. All of them in preclinical phase trials are used in animal models, mainly mice [85,98]. As for other virus diseases, apparently the best choice for anti-CHIKV vaccination is a strategy using an attenuated live virus vaccine, and there are developed candidates. For instance, two mutant virus strains, with large deletions in either the nsP3 gene or in the entire 6K gene, proved to be genetically stable, attenuated, highly immunogenic, and able to confer durable immunity after a single immunization in mice [99]. Neutralizing antibodies recognize the epitopes in the E2 glycoprotein and therefore E2 is another vaccine candidate [100].

Besides, efforts have been made in order to improve vector control strategies. Implementa‐ tion research has been conducted in LAC in order to find ways to improve use of preven‐ tion tools such as insecticide-treated nets and covers, education, social mobilization, and water storage cleaning [101,102]. The potential to prevent and control not only CHIK, but to dengue and Zika too, encourages to direct efforts in order to grant vector control. Like‐ wise, recent studies have shown that vector co-infection with the bacterium *Wolbachia pipientis* impedes virus infection. This bacterium is maternally inherited and is a promising technolo‐ gy to control disease spread [103].

#### **Author details**

Alfonso J. Rodriguez-Morales1,2,3,4,5\*, Jaime Andrés Cardona-Ospina1 and Wilmer E. Villamil-Gómez2,5,6

\*Address all correspondence to<EMAIL_ADDRESS>
1 Public Health and Infection Research Group, School of Medicine and School of Veterinary Medicine and Zootechnics, Faculty of Health Sciences, Universidad Tecnológica de Pereira, Pereira, Risaralda, Colombia

2 Committee on Zoonoses and Haemorrhagic Fevers, Asociación Colombiana de Infectología, Bogotá, DC, Colombia

3 Working Group on Zoonoses, International Society for Chemotherapy, Aberdeen, United Kingdom

4 Colombian Collaborative Network on Zika (RECOLZIKA), Pereira, Risaralda, Colombia

5 Infectious Diseases and Infection Control Research Group, Hospital Universitario de Sincelejo, Sincelejo, Sucre, Colombia

6 Programa del Doctorado de Medicina Tropical, Universidad de Cartagena, Cartagena, Universidad del Atlántico, Barranquilla, Colombia

#### **References**

[1] Pan American Health Organization. Chikungunya Situation in the Americas 2014 [cited 2016 22/02]. Available from: http://www.paho.org/hq/index.php?op‐ tion=com\_topics&view=readall&cid=5855&Itemid=40931&lang=en.

[2] Cardona-Ospina JA, Diaz-Quijano FA, Rodríguez-Morales AJ. Burden of chikungu‐ nya in Latin American countries: estimates of disability adjusted life years (DALY) lost in 2014 epidemic. Int J Infect Dis. 2015; 38:60-61.

antibodies recognize the epitopes in the E2 glycoprotein and therefore E2 is another vaccine

Besides, efforts have been made in order to improve vector control strategies. Implementa‐ tion research has been conducted in LAC in order to find ways to improve use of preven‐ tion tools such as insecticide-treated nets and covers, education, social mobilization, and water storage cleaning [101,102]. The potential to prevent and control not only CHIK, but to dengue and Zika too, encourages to direct efforts in order to grant vector control. Like‐ wise, recent studies have shown that vector co-infection with the bacterium *Wolbachia pipientis* impedes virus infection. This bacterium is maternally inherited and is a promising technolo‐

1 Public Health and Infection Research Group, School of Medicine and School of Veterinary Medicine and Zootechnics, Faculty of Health Sciences, Universidad Tecnológica de Pereira,

3 Working Group on Zoonoses, International Society for Chemotherapy, Aberdeen, United

4 Colombian Collaborative Network on Zika (RECOLZIKA), Pereira, Risaralda, Colombia

6 Programa del Doctorado de Medicina Tropical, Universidad de Cartagena, Cartagena,

[1] Pan American Health Organization. Chikungunya Situation in the Americas 2014 [cited 2016 22/02]. Available from: http://www.paho.org/hq/index.php?op‐

tion=com\_topics&view=readall&cid=5855&Itemid=40931&lang=en.

5 Infectious Diseases and Infection Control Research Group, Hospital Universitario de

2 Committee on Zoonoses and Haemorrhagic Fevers, Asociación Colombiana de

and

candidate [100].

10 Current Topics in Chikungunya

**Author details**

gy to control disease spread [103].

Wilmer E. Villamil-Gómez2,5,6

Pereira, Risaralda, Colombia

Kingdom

**References**

Infectología, Bogotá, DC, Colombia

Sincelejo, Sincelejo, Sucre, Colombia

Universidad del Atlántico, Barranquilla, Colombia

Alfonso J. Rodriguez-Morales1,2,3,4,5\*, Jaime Andrés Cardona-Ospina1

\*Address all correspondence to<EMAIL_ADDRESS>

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## **Chikungunya Fever During Pregnancy and in Children: An Overview on Clinical and Research Perspectives**

Patrick Gérardin, A. Désirée LaBeaud, Nicole Ritz and Xavier Fritel

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/64424

#### **Abstract**

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TMAID-D-16-00072R1) doi: 10.1016/j.tmaid.2016.06.004

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Chikungunya fever (CF) is an arboviral disease in worldwide expansion due to the plasti‐ city of its pathogen and vector. Chikungunya virus (CHIKV), a positive-sense, singlestranded RNA alphavirus, is transmitted by *Aedes* (*Stegomyia*) *aegypti* and *Aedes albopictus* mosquitoes, two hegemonic anthropophilic day-biting mosquitoes capable of colonizing very different environments. This expert review discusses the molecular epidemiology, pathophysiology, clinical features, diagnosis, management, and prevention of CF during pregnancy, infancy, and childhood. Specifically, it will focus not only on the issue and challenges of perinatal mother-to-child transmission of CHIKV, its pathogenesis, and ef‐ fects on neurodevelopment, but also on CHIKV-associated central nervous system dis‐ ease in children, two previously ill-characterized features of the infection.

**Keywords:** Chikungunya virus, children, encephalitis, epidemiology, pregnancy

#### **1. Introduction**

Chikungunya fever (CF) is an arthropod-borne viral disease caused by the chikungunya virus (CHIKV) [1]. First described during an outbreak of dengue-like illness in the Newala district of the southern province of Tanganiyika (current Tanzania) in 1952–1953, the virus derives its name from the Makonde language and means "to become contorted" or "that which bends up" [2, 3]. These descriptors refer to the hallmark of the disease observed in adults, namely, severe incapacitating arthralgia, which was characterized as "frightening" in the seminal description of Robinson [4], as they lead to an inability to stand or walk [5]. In the majority of adult patients with CF, painful arthritis can continue for months and even years, yielding a significant persistent disease burden in affected populations [6–9]. CF is usually not lifethreatening, although atypical and severe forms can occur during large-scale epidemics and

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

a slight increase of mortality has accompanied the peak of the outbreak in La Réunion island [10–15]. Indeed, CHIKV-associated mortality is considered rare (~1‰ infections), but occurs primarily among the elderly, as evidenced in La Réunion, India, or in Puerto Rico [15–17].

Genome-scale phylogenetic analyses of CHIKV suggest that the virus originated from Africa and was subsequently introduced from Africa into Asia [18]. Phylogenetically, CHIKV has evolved into three distinct clades across the past five centuries: Asian, East Central South African (ECSA), and West African lineages.

In its natural cycle, CHIKV is transmitted by the bite of female arboreal *Aedes* (*Stegomyia*) mosquitoes. The peridomestic *Ae. aegypti*, the well-known vector of yellow fever and dengue, was identified as the primary vector of CHIKV during its inaugural outbreaks, both in Africa [2] and Asia [19]. It is only during the last decade that *Ae. albopticus* (also known as the Asian tiger mosquito) has been recognized as a new propagating vector of CHIKV [20]. Originally native to Southeast Asia, *Ae. albopticus* has adapted successfully to cooler climates and spread worldwide [21]. Alongside the broadening geographic distribution of this new hegemonic vector, genetic adaptation through mutations in the envelope glycoproteins E1 and E2 has led to increased infectivity and dissemination of CHIKV in *Ae. albopictus* [22]. Moreover, rapidly increasing international travel exposures has contributed to the global expansion of CF. Over the last decade, ECSA CHIKV has been responsible for most of the recorded cases worldwide; however, in late 2013 somewhat surprisingly Asian CHIKV emerged in the Caribbean island of Saint-Martin [23] and further spread to the neighboring islands and to the Americas, causing over 1.6 million cases by November 13, 2015 [24].

In addition to horizontal mosquito-borne transmission, CHIKV can also be transmitted vertically, and mother-to-child transmission of CHIKV infection often leads to severe neonatal disease, mostly encephalitis, that may cause lifelong disabilities [25]. This expert review will discuss the molecular epidemiology, pathophysiology, clinical features, diagnosis, manage‐ ment, and prevention of CF in the pregnant woman and in children, with a particular focus on the issue and challenges of congenital infection.

### **2. Molecular epidemiology**

#### **2.1. The chikungunya virus**

CHIKV is a positive-sense, single-stranded RNA virus (genus Alphavirus, family Togaviri‐ dae), whose genome encodes at the 5′ extremity four nonstructural proteins (nsP1, nsP2, nsP3, and nsP4 responsible for negative-strand RNA synthesis, helicase and protease activity, RNAdependent RNA polymerase activity, respectively) and at the 3′ extremity three envelope glycoproteins (E1, responsible for membrane fusion; E2, responsible for receptor binding and virulence (E1 and E2 carrying the main epitopes); E3, which serves as a clade-specific signal sequence for translocation of the glycoprotein complex in the endoplasmic reticulum) [26]. The native monomeric capsid is of ∼40 nm diameter and the mature enveloped virion of ∼70 nm, with a genome weighing ∼11.8 kB. In recent years, the ECSA clade has selected the A226V substitution for better fitness to *Ae. albopictus* [27].

#### **2.2. Chikungunya virus life cycle and modes of transmission**

CHIKV is endemic in Africa where it circulates in sylvatic/enzootic cycle between arboreal mosquitoes (*Ae. furcifer*, *Ae. taylori*, *Ae. africanus*, and *Ae. luteocephalus*) and nonhuman primates and bats as reservoir hosts. Birds and other mammals have been found infected, but serve as occasional hosts without amplification of the virus [28]. In this context, the transmission depends on few mosquitoes and is usually clustered to sporadic cases [29].

In epidemic settings, the virus is transmitted by *Ae. albopictus* or *Ae. aegypti*, two day-biting anthropophilic vectors whose peak activity occurs early in the morning or in the evening, around or within human dwellings [20]. During the blood meal, *Aedes* mosquitoes acquire the virus from an infected person. In the subsequent extrinsic phase, the virus multiplies in the gut and migrates to the salivary glands (≥2 days depending on temperature) [30].  *Aedes* spp. mosquitoes remain infectious throughout their whole life (30–45 days). Transmission between nonimmune human hosts is often massive and both sustained by densities of host and vector populations, very high titer viremias in humans, as well as by lack of protective host behaviors [29].

#### **3. Pathophysiology**

a slight increase of mortality has accompanied the peak of the outbreak in La Réunion island [10–15]. Indeed, CHIKV-associated mortality is considered rare (~1‰ infections), but occurs primarily among the elderly, as evidenced in La Réunion, India, or in Puerto Rico [15–17]. Genome-scale phylogenetic analyses of CHIKV suggest that the virus originated from Africa and was subsequently introduced from Africa into Asia [18]. Phylogenetically, CHIKV has evolved into three distinct clades across the past five centuries: Asian, East Central South

In its natural cycle, CHIKV is transmitted by the bite of female arboreal *Aedes* (*Stegomyia*) mosquitoes. The peridomestic *Ae. aegypti*, the well-known vector of yellow fever and dengue, was identified as the primary vector of CHIKV during its inaugural outbreaks, both in Africa [2] and Asia [19]. It is only during the last decade that *Ae. albopticus* (also known as the Asian tiger mosquito) has been recognized as a new propagating vector of CHIKV [20]. Originally native to Southeast Asia, *Ae. albopticus* has adapted successfully to cooler climates and spread worldwide [21]. Alongside the broadening geographic distribution of this new hegemonic vector, genetic adaptation through mutations in the envelope glycoproteins E1 and E2 has led to increased infectivity and dissemination of CHIKV in *Ae. albopictus* [22]. Moreover, rapidly increasing international travel exposures has contributed to the global expansion of CF. Over the last decade, ECSA CHIKV has been responsible for most of the recorded cases worldwide; however, in late 2013 somewhat surprisingly Asian CHIKV emerged in the Caribbean island of Saint-Martin [23] and further spread to the neighboring islands and to the Americas, causing

In addition to horizontal mosquito-borne transmission, CHIKV can also be transmitted vertically, and mother-to-child transmission of CHIKV infection often leads to severe neonatal disease, mostly encephalitis, that may cause lifelong disabilities [25]. This expert review will discuss the molecular epidemiology, pathophysiology, clinical features, diagnosis, manage‐ ment, and prevention of CF in the pregnant woman and in children, with a particular focus

CHIKV is a positive-sense, single-stranded RNA virus (genus Alphavirus, family Togaviri‐ dae), whose genome encodes at the 5′ extremity four nonstructural proteins (nsP1, nsP2, nsP3, and nsP4 responsible for negative-strand RNA synthesis, helicase and protease activity, RNAdependent RNA polymerase activity, respectively) and at the 3′ extremity three envelope glycoproteins (E1, responsible for membrane fusion; E2, responsible for receptor binding and virulence (E1 and E2 carrying the main epitopes); E3, which serves as a clade-specific signal sequence for translocation of the glycoprotein complex in the endoplasmic reticulum) [26]. The native monomeric capsid is of ∼40 nm diameter and the mature enveloped virion of ∼70 nm, with a genome weighing ∼11.8 kB. In recent years, the ECSA clade has selected the A226V

African (ECSA), and West African lineages.

20 Current Topics in Chikungunya

over 1.6 million cases by November 13, 2015 [24].

on the issue and challenges of congenital infection.

substitution for better fitness to *Ae. albopictus* [27].

**2. Molecular epidemiology**

**2.1. The chikungunya virus**

The onset of CF coincides with viremia (median duration: 5 days; range: 2–12 days). The mechanisms underlying acute CHIKV infection are still imperfectly understood [1]. Based on several animal models and meta-analysis of human immune signatures, once introduced into the dermis, it is believed that CHIKV disseminates in blood circulation causing a Th1-cytokine storm [31, 32]. CHIKV replicates in the liver hosted by endothelial and Küpffer cells, before reaching joint fibroblasts, muscle satellite, and skin epithelial cells, causing arthralgia, myalgia, and rash. Indeed, elective targeted sites where symptoms focus are typically infected, espe‐ cially joint capsules, skeletal muscles, myotendinous insertions, and epidermis [1].

The intensity of the acute infection correlates with the CHIKV viral load [1]. The ability of CHIKV to disseminate through the body to the target organs is inversely correlated to the height of the host type-1 interferon (IFN) response. There is evidence that this CHIKV-specific innate immune response depends on the age and the maturity of the human host [33]. This can be shown in vulnerable persons by the breaking of two natural protective barriers, the blood brain barrier (BBB) and the skin barrier. Thus, infants and individuals >65 years of age are likely to exhibit severe or atypical localizations, including CHIKV-associated central nervous system (CNS) disease and severe bullous skin lesions. For example, the incidence of CHIKV-associated encephalitis is best described by an asymmetric U-shaped parabolic curve with the highest incidence occurring in infants below 6 months of age, the nadir being reached in young children (1–4 years of age), and a rise in seniors (≥65 years of age) to a figure fivefold lower than in infants [34]. Furthermore, skin blistering (rupture of bullous lesions) is almost exclusively observed in infants below 6 months of age [35].

B cells and neutralizing antibodies (abs) are critical for CHIKV clearance. Targeted epitopes for anti-CHIKV abs are located at C terminus of the E2 glycoprotein [36]. The contribution of lymphoid (CD4 and CD8) and other cell types responsible for the adaptive immunity could be critical in residual arthralgia. Their immaturity may explain the rarity of chronic arthralgia before the age of 3 years. The role of myeloid cells is less clear in the acute and chronic stage of human CHIKV infection. At the acute stage, blood monocytes may be able to disseminate the virus toward the target tissues [37]. At the chronic stage, myeloid cells may be involved in the clearance of infected cell debris but whether CHIKV replication, lack of virus antigen clearance, or both contribute to rheumatism deserves further studies.

The long-term persistence of CHIKV in tissue macrophages (aka "host sanctuaries") as main driver for chronic inflammation has been postulated from a single clinical observation [38]. It is supported by the data from several animal models (i.e., "for example, see [31]").

### **4. Clinical features**

#### **4.1. Chikungunya fever during pregnancy**

Pregnancy, a situation physiologically oriented toward a Th2-lymhocyte shift [39], has not been associated as a condition precipitating severe forms of infection in CF [40].

The consequences for the mother and the fetus of a CHIKV infection acquired during preg‐ nancy have been investigated extensively on La Réunion island, both in the Groupe Hospitalier Sud-Reunion cohort study [41, 42], in the CHIMERE ("Chikungunya Mère-Enfant") cohort study [43], and in the 2004–2006 Family Allowance Office (41,665 deliveries) and Mother and Child Welfare (42,259 neonates) records [44]. To date, there is no reliable epidemiological data linking CHIKV exposure in the first trimester of gestation to an increased risk for miscarriage, nor to any type of congenital malformation [43, 44].

In the second trimester, CHIKV infection has been associated with only three cases of ante‐ partum fetal deaths without clear evidence for the mechanism [45]. The CHIKV crossing of the placenta may be accidental and the timing of the infections (12 weeks + 4 days, 15 weeks, and 15 weeks + 5 days) coincides in the woman with the period of deep trophoblast invasion. We hypothesize Toll-like receptor (TLR) 3 expression and Th1 cytokines associated with CHIKV infection could have disturbed the spiral arteries remodeling, characteristic of this particular period. Our hypothesis is supported by the involvement of TLR3 in both the susceptibility to CHIKV infection and the impairment of vascular remodeling or fetal losses, as demonstrated in mouse models [46, 47].

In the third trimester, although 14 cases of stillborn fetuses have been reported associated with CF in pregnant women cohorts [42, 43], none was positive for CHIKV, which supports the nonpermissiveness of the human syncytiotrophoblast to CHIKV, as suggested by data from the IFN-α/βR–/– mouse model and the absence of infection of BeWo cell line [33]. These findings are strengthened by the data retrieved from French population-based records [44]. The contribution of subclinical premature placental abruption has been proposed to support the exceptional cases of prepartum CHIKV infection in preterm neonates [48].

Importantly, CHIKV can be transmitted vertically with a probability ~50%, when the parturi‐ ent woman has a high viral load during the early stage of labor [41–43]. Fetal heart rate decelerations and meconium-stained amniotic fluid are common during labor [42, 49]. Neither postponing delivery nor cesarean has been shown to be protective. In this context, the alleged mechanism to explain the transmission to the neonate is the breakdown of the syncytiotro‐ phoblast due to uterine contractions (aka the "placental breeches" hypothesis) [42] while placental microtransfusion has not been ruled out by a proper scientific investigation.

lymphoid (CD4 and CD8) and other cell types responsible for the adaptive immunity could be critical in residual arthralgia. Their immaturity may explain the rarity of chronic arthralgia before the age of 3 years. The role of myeloid cells is less clear in the acute and chronic stage of human CHIKV infection. At the acute stage, blood monocytes may be able to disseminate the virus toward the target tissues [37]. At the chronic stage, myeloid cells may be involved in the clearance of infected cell debris but whether CHIKV replication, lack of virus antigen

The long-term persistence of CHIKV in tissue macrophages (aka "host sanctuaries") as main driver for chronic inflammation has been postulated from a single clinical observation [38]. It

Pregnancy, a situation physiologically oriented toward a Th2-lymhocyte shift [39], has not

The consequences for the mother and the fetus of a CHIKV infection acquired during preg‐ nancy have been investigated extensively on La Réunion island, both in the Groupe Hospitalier Sud-Reunion cohort study [41, 42], in the CHIMERE ("Chikungunya Mère-Enfant") cohort study [43], and in the 2004–2006 Family Allowance Office (41,665 deliveries) and Mother and Child Welfare (42,259 neonates) records [44]. To date, there is no reliable epidemiological data linking CHIKV exposure in the first trimester of gestation to an increased risk for miscarriage,

In the second trimester, CHIKV infection has been associated with only three cases of ante‐ partum fetal deaths without clear evidence for the mechanism [45]. The CHIKV crossing of the placenta may be accidental and the timing of the infections (12 weeks + 4 days, 15 weeks, and 15 weeks + 5 days) coincides in the woman with the period of deep trophoblast invasion. We hypothesize Toll-like receptor (TLR) 3 expression and Th1 cytokines associated with CHIKV infection could have disturbed the spiral arteries remodeling, characteristic of this particular period. Our hypothesis is supported by the involvement of TLR3 in both the susceptibility to CHIKV infection and the impairment of vascular remodeling or fetal losses,

In the third trimester, although 14 cases of stillborn fetuses have been reported associated with CF in pregnant women cohorts [42, 43], none was positive for CHIKV, which supports the nonpermissiveness of the human syncytiotrophoblast to CHIKV, as suggested by data from the IFN-α/βR–/– mouse model and the absence of infection of BeWo cell line [33]. These findings are strengthened by the data retrieved from French population-based records [44]. The contribution of subclinical premature placental abruption has been proposed to support the

Importantly, CHIKV can be transmitted vertically with a probability ~50%, when the parturi‐ ent woman has a high viral load during the early stage of labor [41–43]. Fetal heart rate

exceptional cases of prepartum CHIKV infection in preterm neonates [48].

is supported by the data from several animal models (i.e., "for example, see [31]").

been associated as a condition precipitating severe forms of infection in CF [40].

clearance, or both contribute to rheumatism deserves further studies.

**4. Clinical features**

22 Current Topics in Chikungunya

**4.1. Chikungunya fever during pregnancy**

nor to any type of congenital malformation [43, 44].

as demonstrated in mouse models [46, 47].

There is no increased risk to the pregnant mother for hypertensive disorders, gestational diabetes mellitus, or intrauterine growth restriction associated with maternal CF [43, 44, 50]. The relationships between average fetal birthweight, small-for-gestational age, and the timing of maternal CF during pregnancy are displayed in Figure 1.

*Liveborn neonates were matched on birth gestational age and further compared according to the timing of maternal chikungunya fever during pregnancy. There was no statistical difference between exposed (purple) and unexposed (green) neonates in terms of small-for-gestational age incidence and the only observed difference was a non-clinically relevant lower mean birthweight in neo‐ nates exposed in the second trimester of pregnancy (\*).*

**Figure 1.** Average fetal birthweight, small-for-gestational age and the timing of maternal CF during pregnancy, Reun‐ ion island 2006 (i.e., "for details see [50].").

Contrary to dengue [51, 52], there is also no increased risk for obstetric hemorrhage (placental abruption), preterm birth or low birthweight [43, 44, 50].

#### **4.2. Chikungunya fever in the neonate ("congenital chikungunya")**

Perinatal mother-to-child CHIKV infection was first reported during La Réunion island outbreak in year 2005 [53]. It has been investigated extensively on the island using both a retrospective regional case series [54] and two prospective hospital-based cohort studies, one on a local basis, the GHSR child cohort study [42], and the other on a regional basis, the "CHIMERE child" cohort study [55, 56].

Children who are prenatally infected with CHIKV are born with very low or even undetectable viremia, which makes the hypothesis of placental microtransfusion unlikely as the expected neonatal viremia would parallel the one of the mother. On average, it takes 4–5 days (range: 3–7 days) for the viral load of CHIKV transmitted at birth to reach a level significant enough to cause clinical disease. Neonatal CHIKV infection almost invariably presents with fever, pain, and suckling difficulties often requiring enteral or parenteral nutrition [42]. Other common symptoms include limb edema, *petechiae*, and a skin rash such as maculopapular rash and intertriginous aphthous-like ulcers [25]. Further clinical features of neonatal CHIKV infection, although relatively infrequent in this age group, are cyanosis (slate coloration) and hyperpig‐ mentation of the skin [35, 50, 55, 57–61]. Their topography includes centro-facial area (nose, lips), trunk, abdomen, extremities, and knuckles. Hyperpigmentation may persist for several weeks to months. Vesiculobullous skin lesions are exceptional [62]. Thrombocytopenia, lymphopenia, and mild to moderate increases of serum aspartate aminotransferase (AST or SGOT) are frequent observations [42, 54, 57–61].

Life-threatening complications occur in half of the neonates and display two main clinical pictures: CHIKV-associated CNS disease (formerly reported as encephalopathy) that in fact consists of an encephalitis [34] and a multiple organ dysfunction (MOD) syndrome that combines a circulatory collapse (hypovolemia and hyperkinetic profile on echocardiography), lethargy, hemorrhages (disseminated intravascular coagulation), uremia, and cytolysis [59]. These severe manifestations require intensive care support including mechanical ventilation (for airway protection or neurosedation) in a quarter of neonates, vasoactive amines, and platelet and red blood cell transfusions. Risk factors for severe disease are immaturity and low birthweight. Indicators for severity include a reduced core to skin temperature, low prothrom‐ bin rate, and low platelet count [42].

The most characteristic magnetic resonance imaging (MRI) findings of the early acute stage (day 7), subacute stage (day 30), and chronic stage (day 120) of CHIKV-associated encephalitis are presented in Figure 2.

Changes in the course of cerebral edema and the passage from the cytotoxic to the vasogenic phase occur around day 10 of onset of neurologic symptoms and may be monitored by transfontanellar ultrasonography using velocimetry for measuring the blood flow in the anterior cerebral artery trunks (pericallosal and calloso-marginal arteries). Other neuroradio‐ logic features include scattered supratentorial parenchymal lesions such as basal ganglia and subcortical area bleeding, but also the possibility of cerebellar hematoma, as a reversible consequence of DIC syndrome [42, 55, 60].

Chikungunya Fever During Pregnancy and in Children: An Overview on Clinical and Research Perspectives http://dx.doi.org/10.5772/64424 25

**4.2. Chikungunya fever in the neonate ("congenital chikungunya")**

"CHIMERE child" cohort study [55, 56].

24 Current Topics in Chikungunya

SGOT) are frequent observations [42, 54, 57–61].

bin rate, and low platelet count [42].

consequence of DIC syndrome [42, 55, 60].

are presented in Figure 2.

Perinatal mother-to-child CHIKV infection was first reported during La Réunion island outbreak in year 2005 [53]. It has been investigated extensively on the island using both a retrospective regional case series [54] and two prospective hospital-based cohort studies, one on a local basis, the GHSR child cohort study [42], and the other on a regional basis, the

Children who are prenatally infected with CHIKV are born with very low or even undetectable viremia, which makes the hypothesis of placental microtransfusion unlikely as the expected neonatal viremia would parallel the one of the mother. On average, it takes 4–5 days (range: 3–7 days) for the viral load of CHIKV transmitted at birth to reach a level significant enough to cause clinical disease. Neonatal CHIKV infection almost invariably presents with fever, pain, and suckling difficulties often requiring enteral or parenteral nutrition [42]. Other common symptoms include limb edema, *petechiae*, and a skin rash such as maculopapular rash and intertriginous aphthous-like ulcers [25]. Further clinical features of neonatal CHIKV infection, although relatively infrequent in this age group, are cyanosis (slate coloration) and hyperpig‐ mentation of the skin [35, 50, 55, 57–61]. Their topography includes centro-facial area (nose, lips), trunk, abdomen, extremities, and knuckles. Hyperpigmentation may persist for several weeks to months. Vesiculobullous skin lesions are exceptional [62]. Thrombocytopenia, lymphopenia, and mild to moderate increases of serum aspartate aminotransferase (AST or

Life-threatening complications occur in half of the neonates and display two main clinical pictures: CHIKV-associated CNS disease (formerly reported as encephalopathy) that in fact consists of an encephalitis [34] and a multiple organ dysfunction (MOD) syndrome that combines a circulatory collapse (hypovolemia and hyperkinetic profile on echocardiography), lethargy, hemorrhages (disseminated intravascular coagulation), uremia, and cytolysis [59]. These severe manifestations require intensive care support including mechanical ventilation (for airway protection or neurosedation) in a quarter of neonates, vasoactive amines, and platelet and red blood cell transfusions. Risk factors for severe disease are immaturity and low birthweight. Indicators for severity include a reduced core to skin temperature, low prothrom‐

The most characteristic magnetic resonance imaging (MRI) findings of the early acute stage (day 7), subacute stage (day 30), and chronic stage (day 120) of CHIKV-associated encephalitis

Changes in the course of cerebral edema and the passage from the cytotoxic to the vasogenic phase occur around day 10 of onset of neurologic symptoms and may be monitored by transfontanellar ultrasonography using velocimetry for measuring the blood flow in the anterior cerebral artery trunks (pericallosal and calloso-marginal arteries). Other neuroradio‐ logic features include scattered supratentorial parenchymal lesions such as basal ganglia and subcortical area bleeding, but also the possibility of cerebellar hematoma, as a reversible

*At day 7 of life, diffusion-weighted imaging (DWI) reveals scattered hyper-intensity signals of the white matter (WM), as marked in the frontal lobe (red star) or in the posterior arm of the corpus callosum (red arrows) evocative of cytotoxic edema (A), apparent diffusion coefficient (ADC) reveals low-output areas (blue) of restriction evocative of parenchymal ischemia (B). At day 30, DWI reveals scattered hypo-intensity signals of the WM in the same areas evocative of vasogenic edema (C), ADC reveals high-output areas of reperfusion (red) evocative of blood brain barrier leakage (D). At day 120, T2-weighted (T2W) and T1-weighted imaging (T1-W1) reveal a scattered scalloped appearance of the WM (blue star), a dilatation of the interhemispheric sulcus (double blue arrow) indicative of WM mass reduction (E,F), focused in the frontal (blue oval) lobe (G), monovoxel spectroscopy reveals a lower N-acetyl aspartate peak signal (red arrow) in the left posterior parietal lobe (P2) evocative of axonal loss (H).*

**Figure 2.** Typical course of cerebral edema over a 4-month period in a neonate with CHIKV-associated CNS disease previously defined as "severe encephalopathy" [42], reclassified as CHIKV-associated encephalitis [34], Reunion is‐ land, 2006.

Transient coronary arteries dilatation was reported for six neonates [55]. Cardiologic involve‐ ment in this context is evocative of myocardiopathy or myocarditis, it includes left ventricular hypertrophy (sometimes complicated by left ventricular dysfunction or septal dyskinesia) and pericardial effusion [55, 61].

To date, only few CHIKV-associated deaths in neonates have been reported [55, 61, 62]. For the neonates without neurological involvement, recovery was observed in 1–3 weeks without *sequelae*; however, future long-term studies will shed more light on the presence of subtle morbidities related to CF in these infants [63]. The neurodevelopmental outcome associated with perinatal mother-to-child CHIKV infection will be discussed in Section 4.5.

To investigate the potential for serological evidence of congenital infection in apparently healthy neonates born to women infected with CHIKV during pregnancy, we monitored the kinetics of transplacental CHIKV-specific IgG abs within the CHIMERE cohort study [55]. There was no evidence of asymptomatic congenital CHIKV infection as the 590 participating neonates were all negative for CHIKV-specific IgM at birth and the 368 children with CHIKVspecific IgG present at birth had undetectable levels of CHIKV-specific IgG by a mean of 7.7 months (range: 1–24 months). Seroreversion time (i.e., the time needed to clear transplacental IgG from infant blood or the duration until IgG is undetectable) was inversely correlated to the timing of exposure during pregnancy. Preterm-born infants seroversed earlier. Full-term small-for-gestational age seroreversed earlier than full-term normal-for-gestational age neonates (Figure 3).

*These Kaplan-Meier curves illustrate the bodysize-dependent transfer of transplacental CHIKV-specific IgG antibodies: the seropo‐ sitivity rate is lower in the first post-natal year and the seroreversion time is shorter in full-term small-for-gestational age neonates compared to full-term normal-for gestational-age counterparts.*

**Figure 3.** Seroreversion time of transplacental CHIKV-specific IgG antibodies in full-term normal-for-gestational age (NGA) and full-term small-for-gestational age (SGA) infants, CHIMERE study, Reunion island 2008 (i.e., "for more de‐ tails, see [55].").

These data corroborate a time-dependent and size-dependent placental transfer of maternal IgG: the longer the period of exposure to maternal IgG and the larger the placenta, the higher the load of the IgG transferred to the fetus, and the longer the seroreversion time and theo‐ retically the child's individual protection. These issues may be helpful for maternal or postnatal immunization, should a vaccine become available.

#### **4.3. Chikungunya fever in infants**

To the best of our knowledge, only a few case series described the clinical manifestations of postnatally acquired CF in infants [64–71].

The largest pediatric series published to date, from Kerala, India, including 357 suspected and 35 confirmed cases, reported 140 infants of whom 57% had circulatory collapse and 80% febrile seizures [66]. In another series from Kerala including 56 infants with confirmed CHIKV infection, the main symptoms were fever (100%), skin rash (100%), acrocyanosis (75%), diarrhea (41%), atypical febrile seizures (39%), irritability (26%), lethargy/poor feeding (21%), and limb edema (11%) [67]. Note that the authors have dissected the sequence of skin involve‐ ment: abrupt onset of generalized erythematous rash (day 0 to 2 of fever), maculopapular rash (day 2 to 4), vesiculobullous lesions (day 3 to 6), peeling (day 6 to 10), and hypo- or hyperpig‐ mentation (>day 10).

These data have been confirmed in La Réunion island where half of the infants below 6 months of age exhibited vesiculobullous skin lesions [68, 88]. Importantly, besides the susceptibility for neurological complications (six-fold higher incidence rate of encephalitis) [34], these vesiculobullous skin lesions have emerged as the most characteristic finding of CHIKV infection in this age group [25, 70, 72, 73]. Severe perianal involvement is a characteristic localization [67]. Blisters sometimes cover more than 30% of the body surface, and therefore management resembles that of severe burn patients [70]. Mucosal lesions have not been reported to date. Histopathologic examination of the blisters occurring in the course of CHIKV infection reveals intraepidermal cleavage (splitting beneath and within the stratum granulo‐ sum) with CHIKV-specific IgM deposits onto the basal layer or the dermal capillaries. On follow-up, long-term repigmentation is usually observed, sometimes with skin sequelae including discrete peripheral hyperpigmentation and keloid scars.

#### **4.4. Chikungunya fever in children**

There was no evidence of asymptomatic congenital CHIKV infection as the 590 participating neonates were all negative for CHIKV-specific IgM at birth and the 368 children with CHIKVspecific IgG present at birth had undetectable levels of CHIKV-specific IgG by a mean of 7.7 months (range: 1–24 months). Seroreversion time (i.e., the time needed to clear transplacental IgG from infant blood or the duration until IgG is undetectable) was inversely correlated to the timing of exposure during pregnancy. Preterm-born infants seroversed earlier. Full-term small-for-gestational age seroreversed earlier than full-term normal-for-gestational age

*These Kaplan-Meier curves illustrate the bodysize-dependent transfer of transplacental CHIKV-specific IgG antibodies: the seropo‐ sitivity rate is lower in the first post-natal year and the seroreversion time is shorter in full-term small-for-gestational age neonates*

**Figure 3.** Seroreversion time of transplacental CHIKV-specific IgG antibodies in full-term normal-for-gestational age (NGA) and full-term small-for-gestational age (SGA) infants, CHIMERE study, Reunion island 2008 (i.e., "for more de‐

These data corroborate a time-dependent and size-dependent placental transfer of maternal IgG: the longer the period of exposure to maternal IgG and the larger the placenta, the higher the load of the IgG transferred to the fetus, and the longer the seroreversion time and theo‐ retically the child's individual protection. These issues may be helpful for maternal or postnatal

To the best of our knowledge, only a few case series described the clinical manifestations of

*compared to full-term normal-for gestational-age counterparts.*

immunization, should a vaccine become available.

**4.3. Chikungunya fever in infants**

postnatally acquired CF in infants [64–71].

tails, see [55].").

neonates (Figure 3).

26 Current Topics in Chikungunya

As for children in the first year of life, fever is the main symptom in older children and is usually high grade (102/39–104/40 °F/°C) of sudden onset (<24 hours) and single-spiked [25, 64, 65, 74]. Febrile seizures are common but variably present in 14-80% of the cases. They also occur beyond the typical age range of 6 months to 6 years [25, 64, 69, 73, 74]. Other common symptoms accompanying fever include musculoskeletal pain (30–50%), skin rash (>30%), headache (15%), and photophobia (<10%) [25, 68, 74].

In contrast to adults, arthritis is uncommon in children [25, 74]: 9 of 22 (40%) children reported arthralgia and 6 of 22 (27%) reported arthritis during the Vellore epidemic, Tamil Nadu, India [64]. Residual arthralgia or arthritis is also far less frequent than reported in adults. In the TELECHIK population-based cohort study [75], they were reported in ∼6% of children, two years after acute infection. Unfortunately, these data cannot be retrieved from observational studies or case series, either by lack of follow-up or inability to extract the pediatric data.

The most commonly reported skin manifestations were maculopapular exanthema (morbilli‐ form or generalized) [35, 74, 76], pigmentary changes (diffuse or macular) [77], and intertrigi‐ nous aphthous-like ulcers [75]. Itching is common. Vesiculobullous skin lesions are possible but rare beyond 1 year of age [77].

Hemorrhagic manifestations including epistaxis, gum, subconjunctival bleeding, and purpura are observed in ∼10% of pediatric cases [25]. They are less severe than in children dengue fever.

CHIKV-associated sepsis is less common in toddlers (1–2 years) than in infants (<1 year) and exceptional in children (3–18 years) [64, 76, 78]. In infants, circulatory collapse should prompt cardiologic investigation, including echocardiography as cases of acute cardiac failure have been described during CF [79–81] and myocarditis demonstrated in a young adult [82].

Neurological symptoms have been notified in the acute phase of CF in 25–30% of hospitalized children on the island of La Réunion [25, 68, 69, 83] but were also observed in India [64–66, 74, 84–86]. Their burden will be described in the next section.

#### **4.5. Chikungunya-virus-associated central nervous system (CNS) disease**

CHIKV has long been suspected to be a neurovirulent pathogen [86]. Thus, the seminal publications of CHIKV-associated neuropathology came from India [64] and Cambodia [87].

Among the neurological manifestations complicating CHIKV infection, three distinct clinical patterns can be seen: (i) CHIKV-associated CNS disease, namely encephalopathy of chikun‐ gunya origin and CHIKV-associated encephalitis [34, 42]; (ii) CHIKV-associated peripheral nerve disease, including myeloradiculitis and polyradiculoneuritis, and (iii) a putative nonspecific neurobiologic disease (e.g., lethargy, irritability, altered mental status, mild cognitive disorders, fatigue, etc.) not entirely satisfying the two aforementioned conditions and pre‐ sumably resulting from penetration of proinflammatory cytokines through the BBB. Although nonspecific neurological symptoms and CHIKV-associated CNS disease are deemed to be common in children, CHIKV-associated peripheral nerve disease (Guillain-Barré syndrome often referred as acute flaccid paralysis) seems exceptional [74, 87].

Indeed, hospital-based series have identified headaches, seizures, altered mental status such as confusion or delirium, and neck stiffness as common signs of CNS involvement [83, 84]. Status epilepticus, complex seizures, and encephalitis are being reported as the most serious complications of CNS involvement [25]. Importantly, while the overall burden of neurological manifestations seems to increase with age, the incidence of CHIKV-associated CNS disease peaks in children less than 5 years [34]. This is also highlighted by the fact that fatigue or mild neuropsychiatric symptoms (attention difficulties, sleep, memory, or mood disorders) were reported for 84% of school-age children participating to the TELECHIK cohort study, on average 2 years after acute infection [7].

We propose to represent the burden of neurological manifestations of CF in children using a pyramid (Figure 4), as done classically in public health for vector-borne zoonosis [88].

Little is known on the long-term outcome of CHIKV-associated CNS disease [34]. For example, the neurodevelopmental outcome of perinatal mother-to-child CHIKV infection in the CHIMERE cohort study revealed that 51% of infected neonates had a global neurodevelop‐ mental delay (GND; Brunet-Lézine development quotient ≤ 85) at the age of 2 years [56]. The skill areas affected were coordination and language (57%), sociability (36%), and movement/ Chikungunya Fever During Pregnancy and in Children: An Overview on Clinical and Research Perspectives http://dx.doi.org/10.5772/64424 29

*This pyramid presents the incidence data and proportions of clinical forms according to epidemiological standards for reporting the community burden of infectious diseases.*

**Figure 4.** Burden of CHIKV-associated CNS disease in children, Southern Reunion island, 2009 (i.e., "source SERO‐ CHIK, TELECHIK and ENCEPHALCHIK studies, see [11, 7, 34].").

posture (27%). Importantly, CHIKV infection was an independent predictor for GND after adjustment for maternal social status, infant's weight-for-gestational age, and head circum‐ ference, but also when controlling for preterm birth and breastfeeding. Five of the 12 neonates with CHIKV-associated "encephalopathy" developed a microcephaly of whom 4 matched the definition of cerebral palsy. Note that GND was observed in 38% of the CHIKV-perinatally infected neonates in which CNS disease was not previously suspected.

#### **5. Diagnosis**

Hemorrhagic manifestations including epistaxis, gum, subconjunctival bleeding, and purpura are observed in ∼10% of pediatric cases [25]. They are less severe than in children dengue

CHIKV-associated sepsis is less common in toddlers (1–2 years) than in infants (<1 year) and exceptional in children (3–18 years) [64, 76, 78]. In infants, circulatory collapse should prompt cardiologic investigation, including echocardiography as cases of acute cardiac failure have been described during CF [79–81] and myocarditis demonstrated in a young adult [82].

Neurological symptoms have been notified in the acute phase of CF in 25–30% of hospitalized children on the island of La Réunion [25, 68, 69, 83] but were also observed in India [64–66, 74,

CHIKV has long been suspected to be a neurovirulent pathogen [86]. Thus, the seminal publications of CHIKV-associated neuropathology came from India [64] and Cambodia [87].

Among the neurological manifestations complicating CHIKV infection, three distinct clinical patterns can be seen: (i) CHIKV-associated CNS disease, namely encephalopathy of chikun‐ gunya origin and CHIKV-associated encephalitis [34, 42]; (ii) CHIKV-associated peripheral nerve disease, including myeloradiculitis and polyradiculoneuritis, and (iii) a putative nonspecific neurobiologic disease (e.g., lethargy, irritability, altered mental status, mild cognitive disorders, fatigue, etc.) not entirely satisfying the two aforementioned conditions and pre‐ sumably resulting from penetration of proinflammatory cytokines through the BBB. Although nonspecific neurological symptoms and CHIKV-associated CNS disease are deemed to be common in children, CHIKV-associated peripheral nerve disease (Guillain-Barré syndrome

Indeed, hospital-based series have identified headaches, seizures, altered mental status such as confusion or delirium, and neck stiffness as common signs of CNS involvement [83, 84]. Status epilepticus, complex seizures, and encephalitis are being reported as the most serious complications of CNS involvement [25]. Importantly, while the overall burden of neurological manifestations seems to increase with age, the incidence of CHIKV-associated CNS disease peaks in children less than 5 years [34]. This is also highlighted by the fact that fatigue or mild neuropsychiatric symptoms (attention difficulties, sleep, memory, or mood disorders) were reported for 84% of school-age children participating to the TELECHIK cohort study, on

We propose to represent the burden of neurological manifestations of CF in children using a pyramid (Figure 4), as done classically in public health for vector-borne zoonosis [88].

Little is known on the long-term outcome of CHIKV-associated CNS disease [34]. For example, the neurodevelopmental outcome of perinatal mother-to-child CHIKV infection in the CHIMERE cohort study revealed that 51% of infected neonates had a global neurodevelop‐ mental delay (GND; Brunet-Lézine development quotient ≤ 85) at the age of 2 years [56]. The skill areas affected were coordination and language (57%), sociability (36%), and movement/

84–86]. Their burden will be described in the next section.

**4.5. Chikungunya-virus-associated central nervous system (CNS) disease**

often referred as acute flaccid paralysis) seems exceptional [74, 87].

average 2 years after acute infection [7].

fever.

28 Current Topics in Chikungunya

#### **5.1. Differential diagnosis**

Even though viral diseases are a major public health concern, they are not given due recogni‐ tion as a cause of fever in febrile children in resource limited settings [89]. The differential diagnosis of a febrile child or pregnant woman with recent travel to or residency in tropical areas affected by CHIKV is broad and should include malaria, dengue, influenza, hepatitis, typhoid fever, leptospirosis, and rickettsial infections [25]. In addition, in areas, where these pathogens are present, infections with other alphaviruses, flaviviruses, filoviruses, and bunyaviruses should be considered. In infants, staphylococcal scalded skin syndrome [70] and Kawasaki syndrome [90] should additionally be considered and excluded as the two diagnoses require a specific treatment. Among those listed, dengue is the infection most capable of mimicking CF [25]. Clinical signs including fever pattern, arthralgia, and rash cannot reliably be used to distinguish dengue fever from CF [91]. However, rash appears earlier in the course of CF than it does in dengue fever, and dengue fever is more likely to be associated with bleeding. Pregnancy-induced hypertension, placental abruption, and preterm labor are more common in pregnant woman with dengue than with CF [51, 52].

#### **5.2. Virological methods**

After onset of CF, the viral load can rapidly reach up to 108 genome copies per ml of blood (even a maximum of 2.5 × 108 cps/ml in neonates) [1, 42]. During the first 5 days of infection, the CHIKV genome can be detected in the blood by reverse transcription polymerase chain reaction (RT-PCR). The virus may also be detected in the cerebrospinal fluid of children with CHIKV-associated CNS disease [25] and in blisters of infants with bullous skin lesions [62]. RT-PCR can be designed in multiplex assays to detect other arboviruses [92], which can be very useful for triage of patients [1]. Techniques have continuously improved over the years to allow diagnosis in 2 hours with a minimum cutoff for detecting circulating viremia as low as 40 genome copies/ml using a 5 ml blood sample in TaqMan real-time PCR [93].

#### **5.3. Serological methods**

CHIKV-specific IgM and IgG can be detected in serum by enzyme-like-immunosorbent assay (ELISA) immunocapture. CHIKV-specific IgM are detectable from 3 to 8 days after onset of infection (p.o.i.) and may persist for several months to up to 2 years. CHIKV-specific IgG are detectable from 4 to 10 days p.o.i. and may persist for years [1] and potentially lifelong. Although, improvement has diminished the possibility of cross-reactivity of IgG with other viruses of the Semliki antigenic serocomplex, it may still be useful to ensure a reliable diagnosis of CHIKV infection by using IgG seroconversion (increase by a factor ≥4). In areas where CHIKV and other closely related alphaviruses coexist, plaque reduction neutralization testing becomes a necessary adjunct to confirm CHIKV infection [94].

#### **5.4. Diagnostic testing depends on timing of illness onset**

The molecular assays (TaqMan real-time PCR, RT-LAMP assay, and reverse transcription PCR) are more sensitive in the early stage of CF (2–5 days p.o.i.) when CHIKV-specific IgM are not yet detectable. In the later stages of CF (>5 days p.o.i.), CHIKV-specific IgM is more sensitive than PCR. Experts recommend that ELISA IgM be used as an initial screening test followed by one of the molecular assays in samples negative for IgM in the early stage of CF [95].

### **6. Therapeutic options**

#### **6.1. Pregnant women**

diagnosis of a febrile child or pregnant woman with recent travel to or residency in tropical areas affected by CHIKV is broad and should include malaria, dengue, influenza, hepatitis, typhoid fever, leptospirosis, and rickettsial infections [25]. In addition, in areas, where these pathogens are present, infections with other alphaviruses, flaviviruses, filoviruses, and bunyaviruses should be considered. In infants, staphylococcal scalded skin syndrome [70] and Kawasaki syndrome [90] should additionally be considered and excluded as the two diagnoses require a specific treatment. Among those listed, dengue is the infection most capable of mimicking CF [25]. Clinical signs including fever pattern, arthralgia, and rash cannot reliably be used to distinguish dengue fever from CF [91]. However, rash appears earlier in the course of CF than it does in dengue fever, and dengue fever is more likely to be associated with bleeding. Pregnancy-induced hypertension, placental abruption, and preterm labor are more

(even a maximum of 2.5 × 108 cps/ml in neonates) [1, 42]. During the first 5 days of infection, the CHIKV genome can be detected in the blood by reverse transcription polymerase chain reaction (RT-PCR). The virus may also be detected in the cerebrospinal fluid of children with CHIKV-associated CNS disease [25] and in blisters of infants with bullous skin lesions [62]. RT-PCR can be designed in multiplex assays to detect other arboviruses [92], which can be very useful for triage of patients [1]. Techniques have continuously improved over the years to allow diagnosis in 2 hours with a minimum cutoff for detecting circulating viremia as low

CHIKV-specific IgM and IgG can be detected in serum by enzyme-like-immunosorbent assay (ELISA) immunocapture. CHIKV-specific IgM are detectable from 3 to 8 days after onset of infection (p.o.i.) and may persist for several months to up to 2 years. CHIKV-specific IgG are detectable from 4 to 10 days p.o.i. and may persist for years [1] and potentially lifelong. Although, improvement has diminished the possibility of cross-reactivity of IgG with other viruses of the Semliki antigenic serocomplex, it may still be useful to ensure a reliable diagnosis of CHIKV infection by using IgG seroconversion (increase by a factor ≥4). In areas where CHIKV and other closely related alphaviruses coexist, plaque reduction neutralization testing

The molecular assays (TaqMan real-time PCR, RT-LAMP assay, and reverse transcription PCR) are more sensitive in the early stage of CF (2–5 days p.o.i.) when CHIKV-specific IgM are not yet detectable. In the later stages of CF (>5 days p.o.i.), CHIKV-specific IgM is more sensitive than PCR. Experts recommend that ELISA IgM be used as an initial screening test

as 40 genome copies/ml using a 5 ml blood sample in TaqMan real-time PCR [93].

genome copies per ml of blood

common in pregnant woman with dengue than with CF [51, 52].

After onset of CF, the viral load can rapidly reach up to 108

becomes a necessary adjunct to confirm CHIKV infection [94].

**5.4. Diagnostic testing depends on timing of illness onset**

**5.2. Virological methods**

30 Current Topics in Chikungunya

**5.3. Serological methods**

There is no specific treatment for CF. CF in pregnant women should be treated with antipy‐ retics and analgesics to prevent miscarriage, fetal demise, and limit the harmful consequences of fever, as well as this new competing risk for the neurodevelopmental outcome of preterm neonates.

#### **6.2. Children**

As in pregnant women, there is no specific treatment for CF. Management is symptomatic and focuses on adequate hydration, antipyretics, and analgesics (paracetamol/acetaminophen 60– 80 mg/kg/day) [25]. Experts recommend withholding salicylates, steroidal, and nonsteroidal anti-inflammatory drugs (NSAIDs), as they may facilitate bleeding manifestations [73]. In La Réunion island, ibuprofen had been thought to precipitate infant blistering but the association was not statistically significant [96].

There are no antivirals that have been licensed to treat CF. Ribavirin and IFN-α have *in vitro* an antiviral activity against CHIKV [97], the first being able to alleviate chronic arthralgia and swelling [1]; however, neither one is recommended for use due to risk for side effects and nor the other has been tested in children. It is hoped that in the future, safe and effective antivirals will be able to offer specific CHIKV therapy.

Although persistent joint pain may be challenging to manage, NSAIDs together with cortico‐ steroids or methotrexate successfully have been used in adults [25].

Passive immunotherapy has proven efficacious in the cure of CHIKV infections in animal models [98] and is currently being tested in neonates born to viremic mothers (i.e., "see ClinicalTrials.gov number NCT02230163") in French West Indies and French Guiana [1].

#### **7. Prevention**

#### **7.1. Vaccination**

By the end of year 2015, several promising vaccine candidates have reached late preclinical or phase-1 testing and two have been scheduled for phase-2 trials [99]. The licensure of vaccines will be challenging because of difficulties conducting affordable efficacy trials and predicting future markets [1].

#### **7.2. Control of the vector**

Preventive measures include community mobilization for eradication of breeding sites of Ae. mosquitoes [100], which primarily dwell in natural and artificial water-filled container habitats. During epidemics, peridomestic spraying of insecticides by residents and space spraying by vector controls teams are key for reducing adult mosquito populations.

#### **7.3. Individual protection against mosquito bites**

Appropriate clothing (long clothes for gardening and evening walks) may minimize skin exposure. Insect repellents containing DEET (N,N-diethyl-3-methylbenzamide), IR3535 (3-[Nacetyl-N-butyl]-aminopropionic acid ethyl ester), or picaridin (1-piperidinecarboxylic acid and 2-(2-hydroxyethyl)-1-methylpropylester) are effective [101]. DEET is safe for use in pregnancy, though it is known to cross the placenta, and can be used in children of 3 months of age and older [102]. Its putative neurotoxicity remains controversial [103]. In addition, insecticide-treated nets are important for pregnant women, infants, and children who take daytime naps. Indeed, rest under treated nets for acute patients should be considered as a pillar of community protection and in the hospital setting during the period of viremia for at least 2 weeks. The effectiveness of both types of mechanical preventive measures has not been assessed.

#### **8. Conclusions and perspectives**

CF is a tropical arthropod-borne virus infection whose geographical distribution has grown steadily over the last decade as a result of global warming and globalization of transports. CHIKV can also be transmitted vertically from mother-to-child during the perinatal period when the parturient woman is highly viremic during labor. In the pediatric population, severe forms of CF may occur, and the CNS is particularly affected with encephalitis as the major syndrome of CHIKV-associated CNS disease. At pediatric ages, neonates and small infants below 6 months of age have the highest risk for case fatality and lifelong disabilities.