this may indicate treatment failure or re-infection; the treatment is typically repeated. who guidelines says that any presumed treatment failures at 4 weeks require macrolide resistance testing. secondary yaws in the left armpit of a ten-year-old, 2020 same person, 2 weeks and 3.5 months after a single-dose azithromycin before and two weeks after a single injection of benzathine penicillin, 1950s. epidemiology countries with yaws, currently and previously, as of 2016. where the road ends, yaws begins —who saying, quoted by kingsley asiedu. because t. pallidum pertenue is temperature- and humidity-dependent, yaws is found in humid tropical forest regions in south america, africa, asia and oceania. about three quarters of people affected are children under 15 years of age, with the greatest incidence in children 6–10 years old. therefore, children are the main reservoir of infection. it is more common in remote areas, where access to treatment is poorer. it is associated with poverty and poor sanitation facilities and personal hygiene. worldwide, almost 85% of yaws cases are in ghana, papua new guinea, and the solomon islands. rates in sub-saharan africa are low, but tend to be concentrated in specific populations. as of 2015, it is estimated that about 89 million people live in yaws-endemic areas, but data are poor, and this is likely an over-estimate. in the early 1900s, yaws was very common; in sub-saharan africa, it was more frequently treated than malaria, sometimes making up more than half of treatments. mass treatment campaigns in the 1950s reduced the worldwide prevalence from 50 to 150 million to fewer than 2.5 million; however, during the 1970s there were outbreaks in south-east asia, and there have been continued sporadic cases in south america. as of 2011, it was unclear how many people worldwide were currently infected. from 2008 to 2012, 13 countries reported over 300,000 new cases to the who. there was no system for certifying local elimination of yaws, and it is not known whether the lack of reports from some countries is because they stopped having yaws cases or because they stopped reporting them. it is estimated that if there is not an active surveillance programme, there is less than a 1-in-2 chance that a country will successfully report yaws cases (if it gets them) in over three-quarters of countries with a history of yaws. these countries are thought to need international assistance to mount effective surveillance. generally, yaws is not a notifiable disease. history yaws at the hôpital saint-louis, paris. date: 1806page from surgeon john o'neill's illustrated journal of diseases on west coast of africa, written during his time on hm gun boat decoy. colour diagrams showing a "typical case of framboesia or yaws". date: 1874 examination of remains of homo erectus from kenya, that are about 1.6 million years old, has revealed signs typical of yaws. the genetic analysis of the yaws causative bacteria—treponema pallidum pertenue—has led to the conclusion that yaws is the most ancient of the four known treponema diseases. all other treponema pallidum subspecies probably evolved from treponema pallidum pertenue. yaws is believed to have originated in tropical areas of africa, and spread to other tropical areas of the world via immigration and the slave trade. the latter is likely the way it was introduced to europe from africa in the 15th century. the first unambiguous description of yaws was made by the dutch physician willem piso. yaws was clearly described in 1679 among african slaves by thomas sydenham in his epistle on venereal diseases, although he thought that it was the same disease as syphilis. the causative agent of yaws was discovered in 1905 by aldo castellani in ulcers of patients from ceylon. the current english name is believed to be of carib origin, from "yaya", meaning sore. towards the end of the second world war yaws became widespread in the north of malaya under japanese occupation. after the country was liberated, the population was treated for yaws by injections of arsenic, of which there was a great shortage, so only those with stage 1 were treated. eradication european doctor treats an indonesian woman for yaws, early- to mid-20th-century. after eliminating yaws in india, the indian government releases a report called "yaws elimination in india – a step towards eradication". 2006 yaws before and after treatment with neosalvarsan, an obsolete treatment a series of who yaws control efforts, which began shortly after creation of the who in 1948, succeeded in eradicating the disease locally from many countries, but have not lasted long enough to eradicate it globally. the global control of treponematoses (tcp) programme by the who and the unicef launched in 1952 and continued until 1964. a 1953 questionnaire-based estimate was that there were 50–150 million yaws cases in 90 countries. the global prevalence of yaws and the other endemic treponematoses, bejel and pinta, was reduced by the global control of treponematoses (tcp) programme between 1952 and 1964 from about 50 million cases to about 2.5 million (a 95% reduction). however, "premature integration of yaws and other endemic treponematoses activities into weak primary health-care systems, and the dismantling of the vertical eradication programmes after 1964, led to the failure to finish with the remaining 5% of cases" and led to a resurgence of yaws in the 1970s, with the largest number of case found in the western africa region. following the cessation of this program, resources, attention and commitment for yaws gradually disappeared and yaws remained at a low prevalence in parts of asia, africa, and the americas with sporadic outbreaks. with few cases, mainly affecting poor, remote communities with little access to treatment, yaws became poorly known, yaws knowledge and skills died out even among health professionals, and yaws eradication was not seen as a high priority. although a single injection of long-acting penicillin or other beta lactam antibiotic cures the disease and is widely available and the disease highly localised, many eradication campaigns ended in complacency and neglect; even in areas where transmission was successfully interrupted, re-introduction from infected areas occurred. yaws eradication remained a priority in south-east asia. in 1995, the who estimated 460,000 worldwide cases. in the philippines, yaws stopped being listed as a notifiable disease in 1973; as of 2020, it is still present in the country. india implemented a successful yaws eradication campaign that resulted in the 2016 certification by the who that india was free of yaws. in 1996 there were 3,571 yaws cases in india; in 1997 after a serious elimination effort began the number of cases fell to 735. by 2003 the number of cases was 46. the last clinical case in india was reported in 2003 and the last latent case in 2006; certification by the who was achieved in 2016. in 2012 the who officially targeted yaws for eradication by 2020 following the development of orally administered azithromycin as a treatment, but missed that target. the morges approach (named after morges, switzerland, where a meeting on it was held) involved mass treatment with azithromycin. this was safe, but ran into problems with antibiotic resistance, and did not fully interrupt transmission. the discovery that oral antibiotic azithromycin can be used instead of the previous standard, injected penicillin, was tested on lihir island from 2013 to 2014; a single oral dose of the macrolide antibiotic reduced disease prevalence from 2.4% to 0.3% at 12 months. the who now recommends both treatment courses (oral azithromycin and injected penicillin), with oral azithromycin being the preferred treatment. as of 2020, there were 15 countries known to be endemic for yaws, with the recent discovery of endemic transmission in liberia and the philippines. in 2020, 82,564 cases of yaws were reported to the who, and 153 cases were confirmed. the majority of the cases are reported from papua new guinea and with over 80% of all cases coming from one of three countries in the 2010–2013 period: papua new guinea, solomon islands, and ghana. a who meeting report in 2018 estimated the total cost of elimination to be us$175 million (excluding indonesia). in the south-east asian regional office of the who, regional eradication efforts are focused on the remaining endemic countries in this region (indonesia and east timor) after india was declared free of yaws in 2016. although yaws is highly localized and eradication may be feasible, humans may not be the only reservoir of infection.