crimean - congo hemorrhagic fever ( cchf ) is a fatal infectious disease with an average death rate of 50% .
the disease is caused by the nairovirus group from the bunyaviridae family ( 1 ) and is transmitted through the saliva of blood - sucking arthropods ( ixodidae ticks ) , or by contact with the blood and tissues of infected livestock .
moreover , transmission of cchf virus from person to person may occur by close contact with infected patients or via nosocomial transmission ( 1 - 6 ) .
a number of tick genera are capable of becoming infected with the cchf virus , including hyalomma spp . and rhipicephalus spp . , but the most common vectors appear to be members of the hyalomma genus ( 2 , 6 , 7 ) .
crimean - congo hemorrhagic fever has been reported in 30 countries in africa , the middle east , europe , and asia ( 4 , 8) .
it is prevalent in most of iran s neighboring countries , including pakistan , afghanistan , russia , turkey , iraq , kazakhstan , kuwait , oman , saudi arabia , tajikistan , and the united arab emirates ( 4 ) .
although there had been sporadic reported cases of the disease in livestock and humans since 1970 in iran , the first reported outbreak occurred in 1999 . since that time , cchf has been considered one of the country s major public health challenges ( 3 , 4 ) . currently , cchf is prevalent in 23 of 30 provinces of iran ; sistan - baluchestan , isfahan , fars , and khuzestan are respectively the most heavily - infected provinces ( 4 ) . due to high fatality rates and many challenges in its treatment , prevention , and control ,
cchf is a disease that should be dealt with immediately by public health authorities , so the disease is subject to immediate reporting ( 9 ) .
health center walk - in patients with symptoms of severe headache , sudden onset of high fever , muscular pain , and bleeding should be immediately suspected for cchf ( 9 , 10 ) . in probable cases , thrombocytopenia , leukopenia , and leukocytosis
are detected in the hematological work - up , and are ultimately diagnosed and confirmed by a seropositive test for cchf .
the incubation period of this disease is 1 - 7 days , and onset of disease is usually sudden ( 11 ) . in 2002 , khuzestan province was ranked as having the lowest rate of infection , with 10 or fewer cases annually ( 9 ) .
furthermore , khuzestan is also included as one of the highest - ranking infected areas on this list , with seven probable cases and five confirmed cases ( 4 , 9 ) .
this retrospective study was conducted to investigate the epidemiological aspects of cchf and the determine the disease trend in khuzestan province in 1999 - 2015 .
this survey is a retrospective descriptive study based on statistics from the khuzestan health center during 1999 - 2015 .
various epidemiological parameters , including the annual prevalence of the cchf and the victims age group , occupation , sex , clinical symptoms , living area ( urban or rural ) , and fatality ratio , were collected from the patient - history documents .
the recorded data were analyzed with spss software , and the case - fatality rates were determined using the formula below ( 5 ) .
fatality rate = ( the number of deaths due to cchf during the specific time / total cases of disease during specific time )  100 .
eighty - one patients with cchf symptoms were referred to various health centers in khuzestan province during 1999 - 2015 . among these patients ,
42 were diagnosed as probably cchf - positive with hematological findings positive for thrombocytopenia , of which 17 were confirmed as definite cases with seropositive testing for the cchf virus .
the highest numbers of cases were reported in 2003 and 2010 , with seven cases during each of those years ; there were five death cases in 2003 compared to two in 2010 ( table 1 ) .
however , no cchf was reported in 2007 , 2008 , and 2013 ( figures 1 and 2 ) .
the annual variations of probable , confirmed , and death cases of cchf in khuzestan province during 1999 - 2015 are illustrated in figures 1 and 2 .
the most confirmed cases occurred in 2010 , whereas the most death cases occurred in 2003 , when five out of seven patients died with a probable or confirmed diagnosed .
c , confirmed case ; p , probable case . in 95% of the patients , symptoms of fever , bleeding , and thrombocytopenia were detected .
bleeding was not observed in 5% of the patients , and the nose was the most - bleeding organ ( table 2 ) .
the prevalence of the disease was 45.2% , 26.2% , 14.3% , and 14.3% in the spring , summer , autumn , and winter , respectively .
of all cases , 57.1% of patients were males and 42.9% were females , and 35.7% of patients lived in rural dwellings compared to 64.3% who were from urban areas .
the age groups of 10 - 19 and 20 - 29 years were the highest - risk groups , each with a frequency of 26.2% ( table 3 ) .
the occupational groups most often exposed to cchf were farmers and housewives , with frequencies of 28.6% and 26.2% , respectively ( table 4 ) .
there have been several reports regarding the prevalence of cchf in iran ( 1 - 4 ) . however , it is necessary to calculate the disease incidence and trends in provinces with high rates of infection .
this information provides a better idea and awareness regarding this disease s prevalence , and will better illustrate the efficiency of the organizations involved in disease prevention and surveillance programs .
khuzestan province has been ranked as one of the most heavily - infected provinces ( 4 ) with seven cases in 2003 , of which five led to death . following this outbreak , the disease demonstrated a downward trend from 2004 until 2008 , as there were no reported cases in 2007 and 2008 .
however , an upward trend was noted again in 2009 and 2010 , with seven probable cases reported in 2010 ; four cases were serologically confirmed and two of them eventually died .
the disease followed the same downward trend in iran from 2000 to 2009 ( 4 ) , but it followed an upward trend in turkey during 2002 - 2007 ( 150 cases in 2002 - 2003 compared to 717 in 2007 ) . in iran ,
the highest disease prevalence occurred in 2002 and 2008 , with 111 and 120 confirmed cases , respectively ; of these , 14 and 19 patients died ( 3 ) .
there were no reported cases in khuzestan province in 2008 . in this epidemiological survey of khuzestan province ,
42 probable cchf cases were reported from 1999 to 2015 , of which 64.3% were from urban areas and 35.7% were from rural areas .
the male : female ratio was 1.3:1.0 and the case - fatality ratio was calculated to be 28.6% ( 12/42 ) during this time period .
in a similar epidemiological survey of cchf in turkey during 2002 - 2007 , 1,820 cchf cases were reported and the fatality ratio was calculated to be 5% ( 92/1820 ) , of which 69.4% of patients were from rural areas and the male : female ratio was 1.13:1.00 ( 8) . in iran , 1,638 probable cchf cases were collected from different provinces from june 2000 until december 2009 , of which 635 were confirmed and 89 died ( 4 ) .
therefore , the fatality ratio was calculated to be 5.4% in iran during this time period .
this ratio has a wide range , 2% - 80% , in different countries ( 11 ) .
the case - fatality ratio was 28.6% among 38 persons in mauritania infected with cchf virus from february to august 2003 .
the first patient was a young woman who became ill shortly after butchering a goat ; she transmitted the infection to 15 hospital health workers and four members of her family ( 12 ) . in an assessment of patients with cchf symptoms referred to the amir - almoemenin hospital of zabol county , sistan- baluchestan province , southeast iran , during 2003 - 2005 , a total of 65 patients were enrolled .
of them , 52 ( 80% ) were male and 13 ( 20% ) were female .
the signs and symptoms included fever ( 98.4% ) , headache ( 80% ) , myalgia ( 72.3% ) , nausea and vomiting ( 60% ) , abdominal pain ( 49.2% ) , skin rash ( 13.8% ) , and splenomegaly ( 4% ) . laboratory findings included thrombocytopenia ( 100% ) , leukopenia ( 70.7% ) , and anemia ( 20% ) ( 13 ) . during the first half of 2009 in khorasan razavi province , 13 patients suffered from cchf , which confirmed the upward trend of the disease compared to the same time in previous years .
four patients were health workers , four were butchers , and the others were farmers ( 10 ) . in another epidemiological survey from birjand county , khorasan province , iran , a total of 32 probable cchf patients were hospitalized during 2011 and 2012 .
forty percent of the patients were men and 60% were women . in terms of occupation , 48% of the patients had direct contact with livestock and 70% were from rural areas . in 85% of the cases ,
fever and bleeding were the most common clinical symptoms seen in all of the patients ( 14 ) .
eighty - two probable cases were reported in an epidemiological study of cchf in fars province during 1999 - 2011 , leading to the deaths of 18 patients . of all patients ,
men had the most cases , and the highest - risk occupational groups were farmers , butchers , and slaughterhouse workers .
the most cases were reported in summer and spring , which is the ticks growing season ( 15 ) . two peaks of cchf were observed in khuzestan province during 1999 - 2015 ( in 2003 and 2010 ) , confirming the probability of re - emergence of the disease .
the increased numbers of disease cases in khuzestan in 2010 were attributed to smuggling of cattle and bufflehead , followed by drought in pakistan , afghanistan , and sistan- baluchestan . in the last few decades
, cchf has emerged or re - emerged in various countries due to climate and anthropogenic factors , such as land - use changes , agricultural practices , and movement of livestock , which may influence host - tick - virus dynamics ( 16 ) .
climate changes , unhealthy and illegal slaughter , and smuggling of livestock could also lead to the emergence or re - emergence of the disease , as occurred in many provinces of iran , including khuzestan , in 2010 .
finally , considering that the highest - risk occupational groups for cchf infections are farmers and housewives , and the riskiest age group is 10 - 39 years , these individuals should be instructed and trained with regard to transmission modes , prevention , symptoms , and treatment of cchf .
particular inspections of veterinary organizations with regard to livestock slaughter and trade , treatment of tick - infested livestock , and training of high - risk groups can help reduce the prevalence of cchf in iran .
 backgroundcrimean - congo hemorrhagic fever ( cchf ) is an arboviral zoonotic disease transmitted to humans mainly through the bite of blood - sucking ixodidae ticks and also via contact with the blood and tissues of infected livestock.objectivesthis study is a retrospective descriptive survey based on data collected from the health center of khuzestan province , iran , during 1999 - 2015.patients and methodspatients with symptoms of severe headache , high fever , and bleeding were evaluated . 
 laboratory tests and serological or molecular assays were used to detect probable and confirmed cases , respectively . 
 the epidemiological parameters of this study were analyzed on the basis of probable cases.resultsa total of 42 patients were diagnosed as probable cases , and 17 of these ( 42.5% ) were confirmed serologically . 
 two peaks of the disease occurred in khuzestan province , in 2003 and 2010 , with seven cases each of those years , leading to the deaths of five and two patients , respectively . 
 men and women comprised 57.1% and 42.9% of the patients , respectively . 
 of all probable cases , 64.3% were from urban areas and 35.7% were from rural areas . 
 the age groups of 10 - 19 and 20 - 29 years , with a frequency of 26.2% in each group , were exposed to the most infections . 
 farmers and housewives were the highest at - risk occupational groups with a frequency of 28.6% and 26% , respectively . 
 fever , bleeding , and thrombocytopenia were reported in 95% of the patients , and the case - fatality ratio was calculated to be 28.6% ( 12 of 42 cases).conclusionscontinuous training is necessary to improve the knowledge and awareness of the highest - risk groups with regard to the transmission modes , prevention , symptoms , and treatment of this disease . 
1. Background
2. Objectives
3. Patients and Methods
4. Results
5. Discussion