Yaws: WHO Reports 80+ Countries Reached Elimination Despite 13 Endemic Nations Remaining
Key Facts
- According to WHO, yaws has been eliminated from over 80 countries since the 1950s through mass treatment campaigns, leaving only 13 known endemic countries as of 2024
- WHO data shows an estimated 80,000-120,000 yaws cases remain globally, concentrated primarily in the Pacific islands, West and Central Africa, and Southeast Asia
- A single oral dose of azithromycin achieves cure rates exceeding 95% for yaws, WHO reports, making elimination technically feasible with existing tools
- WHO identifies that yaws affects primarily children aged 5-15 years in impoverished rural communities with limited access to water, sanitation, and healthcare
- According to WHO’s 2021-2030 roadmap on neglected tropical diseases, the target is to eradicate yaws globally by 2030—a goal that remains achievable but requires sustained political commitment
When WHO launched its renewed yaws eradication strategy in 2012, the disease had already been forgotten by most of the world. Once endemic across tropical regions affecting millions, yaws had been driven to the margins through mid-20th-century campaigns using penicillin—then largely abandoned as international health priorities shifted elsewhere. But in the remaining endemic pockets—remote islands in the Pacific, rural communities in West Africa, isolated populations in Southeast Asia—yaws continued its quiet devastation: disfiguring skin lesions, bone deformities, lifelong disability. The 2012 strategy, built on a cheap, single-dose oral antibiotic, offered a genuine path to eradication. Yet more than a decade later, progress has stalled. This article examines what WHO’s data reveals about yaws today, why a disease with a simple cure persists, and whether global health initiatives will muster the will to finish a job that’s 90% complete.
What Is Yaws? — WHO’s Definition
According to WHO, yaws is a chronic disfiguring disease caused by the bacterium Treponema pallidum subspecies pertenue, closely related to the bacterium that causes syphilis but transmitted through skin-to-skin contact rather than sexual contact. Yaws is classified as an endemic treponematosis—a group of chronic bacterial infections that also includes bejel (endemic syphilis) and pinta, all caused by treponemes and affecting primarily impoverished populations with limited access to basic hygiene and healthcare.
WHO frames yaws as a disease of poverty and neglect. It thrives in hot, humid tropical climates where children go barefoot, where overcrowding facilitates skin contact transmission, where water scarcity limits hygiene, and where healthcare infrastructure is minimal or absent. Unlike many neglected tropical diseases that require complex vectors or environmental intermediaries, yaws transmission is straightforward: direct contact between broken skin of an infected person and the skin of a susceptible individual, usually a child.
The key public health insight WHO emphasizes is that yaws is entirely curable with a single dose of antibiotic and causes no mortality—but left untreated, it causes progressive disability including severe bone deformities and tissue destruction that can leave individuals unable to walk or work. It’s a disease that should have been eradicated decades ago. That it persists reflects not biological complexity but failures of political will, resource allocation, and health system reach to the world’s most marginalized populations.
Global Burden
WHO estimates that 80,000-120,000 yaws cases currently exist globally, though the true burden is likely higher due to underreporting in remote endemic areas where surveillance is weak or non-existent. This represents a dramatic reduction from the mid-20th century when an estimated 50-100 million people were infected across 90+ countries. The mass campaigns of the 1950s-1960s, using intramuscular penicillin, reduced global prevalence by over 95% and eliminated yaws from most endemic countries.
But the job wasn’t finished. According to WHO’s neglected tropical disease data (https://www.who.int/news-room/fact-sheets/detail/yaws), 13 countries remain endemic as of 2024: Papua New Guinea, Solomon Islands, Vanuatu, Ghana, Cameroon, Central African Republic, Republic of Congo, Côte d’Ivoire, Democratic Republic of the Congo, Indonesia, Liberia, Togo, and Benin. Papua New Guinea carries the highest burden, accounting for the majority of reported cases globally. The Pacific island nations—Solomon Islands, Vanuatu—have smaller absolute numbers but higher prevalence in affected communities.
The geographic concentration reveals the disease’s social determinants. Endemic areas are remote, impoverished, and politically marginalized. Villages accessible only by boat or foot trail. Communities with no running water, no electricity, no health clinics. Populations that have been neglected not just by disease control programs but by development policy broadly. The pattern mirrors other neglected tropical diseases: just as leishmaniasis persists in marginalized populations despite effective treatments existing, yaws reflects systematic underinvestment in reaching the world’s poorest communities.
Age distribution is distinctive. WHO data shows yaws primarily affects children aged 5-15 years, with peak incidence around ages 6-10. Adults can be infected but less commonly. This age pattern reflects both behavioral factors (children’s greater skin contact through play, barefoot walking) and immunological factors (repeated exposures may confer partial immunity in adults). The concentration in children means yaws impacts education (chronic wounds and disability cause school absences), nutrition (pain and mobility limitations), and lifelong economic productivity when untreated infections cause permanent disability.
Gender distribution is roughly equal, unlike some diseases where biological or social factors create sex-specific patterns. Yaws doesn’t discriminate—it affects boys and girls, men and women equally in endemic communities. What matters is exposure through skin contact, proximity to infected individuals, and lack of access to treatment.
The burden measurement challenges are significant. WHO relies on passive case detection through health facilities and periodic active case-finding surveys in endemic areas. But many infected individuals never reach health facilities due to distance, cost, or lack of awareness. Latent yaws—infection without active skin lesions—is difficult to detect clinically and requires serological testing often unavailable in endemic areas. The result: official case counts are almost certainly underestimates, though by how much is unknown.
Causes, Transmission and Risk Factors
Yaws is caused by Treponema pallidum subspecies pertenue, a spirochete bacterium nearly identical genetically to T. pallidum subspecies pallidum (which causes venereal syphilis) but with distinct epidemiology and transmission. The bacterium enters the body through breaks in the skin—cuts, abrasions, insect bites—during direct contact with infectious skin lesions on an infected person. WHO data indicates the incubation period averages 3-6 weeks from exposure to first symptoms.
Transmission requires direct skin-to-skin contact between an infectious lesion and broken skin. Unlike airborne or waterborne diseases, you can’t catch yaws from contaminated surfaces or fomites—the treponeme doesn’t survive long outside the human body. But in settings where children play together barefoot, sleep together in crowded housing, and have frequent minor skin injuries, transmission is efficient. According to research in PLOS Neglected Tropical Diseases (https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0004008), household and close community contacts show the highest infection risk.
WHO’s risk factor framework identifies both individual and environmental determinants. Individual factors include age (children at highest risk), having open wounds or skin lesions that facilitate bacterial entry, and lack of previous infection (which may confer some immunity). Environmental and social factors are more important: living in tropical humid climates (treponemes thrive in warmth and moisture), poverty limiting access to shoes and protective clothing, overcrowded housing facilitating close skin contact, lack of access to clean water for washing wounds, poor sanitation, and geographic isolation from healthcare services.
Climate is a critical determinant. Yaws is endemic only in tropical regions with consistent warmth and high humidity—the bacterial ecology requires these conditions. Seasonal variation exists, with some studies showing increased transmission during rainy seasons when humidity peaks and skin maceration from wet conditions creates more entry points. But yaws doesn’t have the sharp seasonality of vector-borne diseases; transmission occurs year-round in endemic areas.
The socioeconomic gradient is stark. WHO documentation shows yaws is absent in urban areas and affluent rural communities even within endemic countries. It concentrates in the poorest, most marginalized populations. Why? Not genetic susceptibility—epidemiology shows yaws affects all ethnic groups equally when environmental conditions permit. The determinants are entirely social: poverty, lack of shoes, overcrowding, water scarcity, healthcare access barriers. These are the same social determinants that drive the broader pattern of neglected tropical diseases affecting 1.6 billion people globally—diseases that persist not because we lack tools to control them, but because affected populations lack political power to demand those tools be deployed.
Signs, Symptoms and Health Impacts
WHO identifies three clinical stages of yaws with distinct symptom patterns. Primary yaws begins with a painless papule (raised bump) at the infection site—often on legs or buttocks in children—that enlarges over weeks into a papilloma (raised, raspberry-like lesion) 2-5 cm in diameter. This primary lesion teems with treponemes and is highly infectious. Regional lymph nodes may swell. Without treatment, the primary lesion heals spontaneously after 3-6 months, leaving a scar.
Secondary yaws develops weeks to months after the primary lesion appears (sometimes overlapping). WHO describes multiple secondary manifestations: widespread skin papillomas similar to the primary lesion appearing on face, trunk, and limbs; painful plantar papillomas on the soles of feet (called “crab yaws”) that make walking extremely painful; bone pain and periostitis (inflammation of bone lining) causing swelling and tenderness, particularly in long bones and fingers; and lymphadenopathy (swollen lymph nodes). Secondary lesions are also highly infectious. Like primary lesions, secondary manifestations resolve spontaneously over months, but relapses are common over a 5-year period.
Tertiary yaws emerges years to decades after initial infection in approximately 10% of untreated individuals. WHO identifies devastating late manifestations: destructive gummatous lesions (granulomatous inflammation) that destroy skin, bone, and cartilage; severe bone deformities including tibial bowing (saber shin), nasal bone destruction (gangosa), and joint contractures; disfiguring facial lesions; and chronic plantar hyperkeratosis (thickened, painful soles). These late complications cause permanent disability: inability to walk normally, facial disfigurement causing social stigma, and chronic pain. Unlike venereal syphilis, yaws doesn’t affect cardiovascular or neurological systems—but the skeletal and soft tissue destruction can be equally devastating.
The functional impact is profound. Painful plantar lesions prevent children from walking to school. Bone pain and deformities limit agricultural work in subsistence farming communities. Facial disfigurement creates social isolation and can prevent marriage in some cultural contexts. The disability burden falls primarily on those who were infected as children and never received treatment—a preventable tragedy when a single dose of antibiotic could have achieved cure.
Diagnostic challenges complicate case management. Clinical diagnosis based on characteristic skin lesions is possible for trained health workers, but overlaps with other skin conditions including bacterial skin infections and tropical ulcers. Serological testing—using the same treponemal tests used for syphilis—can confirm treponemal infection but can’t distinguish between yaws, endemic syphilis, pinta, or venereal syphilis. Polymerase chain reaction (PCR) testing can differentiate T. pallidum subspecies but requires laboratory infrastructure unavailable in endemic areas. The result: WHO’s eradication strategy relies primarily on clinical diagnosis supplemented by serological surveys at population level.
Treatment and Health Response
WHO reports that yaws treatment is remarkably simple and effective: a single oral dose of azithromycin (30 mg/kg body weight for children, 2 grams for adults) achieves cure rates exceeding 95%. This represented a major advance over previous treatment with intramuscular benzathine penicillin, which required injection (limiting acceptability and requiring trained personnel) and caused painful reactions. Azithromycin’s oral formulation enables mass drug administration by community health workers without medical training, making large-scale campaigns logistically feasible even in remote areas.
The evidence base is solid. Research published in The Lancet Infectious Diseases (https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(14)70837-8/fulltext) showed that single-dose azithromycin achieved clinical cure in 96% of cases, with lesions healing within weeks and serology converting to negative or declining titers over months. Repeat treatment for the 4-5% who don’t respond achieves cure in nearly all remaining cases. The simplicity is striking: one pill cures a disease that, untreated, causes lifelong disability.
But access to treatment remains the critical barrier. In endemic areas, health facilities are often absent or hours to days distant by foot. Even when facilities exist, azithromycin may not be stocked—it’s not on essential medicines lists in all endemic countries, and supply chains to remote areas are unreliable. Cost is minimal (azithromycin is off-patent and costs pennies per dose in bulk procurement) but still prohibitive for populations living on less than $2 daily. WHO’s strategy addresses this through donated azithromycin from Pfizer and national governments procuring supplies, but distribution to last-mile communities remains challenging.
WHO’s treatment approach centers on two strategies: individual case management (treating diagnosed cases and their contacts) and mass drug administration (MDA) to entire endemic communities. According to WHO guidelines (https://www.who.int/publications/i/item/who-htm-ntd-idn-2012.1), MDA is recommended when community prevalence exceeds 5% of the population (active cases plus latent infections detected by serology). The rationale: treating entire communities interrupts transmission more effectively than trying to identify and treat individual cases in settings where surveillance is weak and many infections are latent.
Regional disparities in treatment access are substantial. Papua New Guinea, with the highest burden, has implemented several rounds of MDA in high-prevalence areas but faces challenges with geographic accessibility (mountainous terrain, isolated islands), population mobility, and health system capacity. Pacific island nations have conducted successful MDA campaigns but struggle with sustained surveillance and retreatment. West African countries face competing health priorities, civil unrest, and limited funding for yaws programs. The parallel to other skin-related neglected tropical diseases is clear: just as Buruli ulcer persists in similar marginalized populations despite known treatments, yaws elimination is constrained more by access than by medical complexity.
Long-term follow-up is inadequate. WHO recommends post-treatment surveillance to detect treatment failures and new cases, but implementation is limited in resource-constrained settings. The risk is that MDA campaigns achieve short-term prevalence reduction but transmission resumes when surveillance and retreatment lapse—exactly what happened in the 1960s-1970s when initial success wasn’t sustained.
Prevention and WHO Strategies
WHO frames yaws eradication as achievable using the “Morges strategy,” named after the 2012 Morges, Switzerland meeting that relaunched elimination efforts. The strategy has three pillars: total community treatment (TCT) with azithromycin in endemic areas, total targeted treatment (TTT) of cases and contacts to prevent transmission, and sustained surveillance to detect and treat any remaining cases until no transmission occurs for three consecutive years.
The TCT approach treats entire communities regardless of infection status when prevalence is high (>5% by serology). This breaks transmission by eliminating the reservoir of latent infections that clinical case-finding misses. WHO recommends repeating TCT rounds every 6 months until prevalence drops below 5%, then transitioning to TTT—active case-finding with treatment of cases and their household/community contacts. The strategy parallels successful approaches for other neglected tropical diseases: treat everyone in endemic areas, drive prevalence down, then switch to surveillance and targeted treatment.
Prevention of new infections requires addressing social determinants WHO has identified: poverty, lack of shoes, overcrowding, and water scarcity. Providing shoes to children in endemic areas could reduce transmission substantially—most primary lesions occur on feet and legs in barefoot children. Improving access to clean water enables wound washing and basic hygiene that prevents bacterial entry. Reducing household overcrowding limits skin contact transmission. These interventions fall outside health sector control and require multi-sectoral development programs that endemic areas have been systematically denied.
There’s no vaccine for yaws. The close antigenic relationship between yaws and syphilis treponemes means a syphilis vaccine, if developed, might protect against yaws—but no treponemal vaccine is near deployment. The eradication strategy relies entirely on treatment-based interruption of transmission, which is feasible given yaws has no animal reservoir and doesn’t persist in the environment. Treat everyone infected, prevent new infections through case detection and treatment, and transmission stops.
Health education is a prevention component. WHO guidance includes community awareness campaigns explaining yaws transmission, encouraging early care-seeking for skin lesions, and promoting hygiene and wound care. But health education without access to treatment and basic services is insufficient—knowing you should wash wounds doesn’t help if you have no water.
Integration with other neglected tropical disease programs offers efficiency gains. Many endemic countries face multiple NTDs. WHO advocates for integrated MDA campaigns that address yaws alongside lymphatic filariasis, trachoma, or soil-transmitted helminth infections—delivering multiple interventions in single community visits. But coordination requires health system capacity that’s often limited in endemic settings.
WHO’s Global Efforts and Eradication Timeline
WHO’s yaws eradication effort has a complex history. The initial campaign from 1952-1964, using benzathine penicillin, treated approximately 160 million people in 46 countries and reduced global prevalence by over 95%. WHO declared yaws “eradicated” or “controlled” in most previously endemic regions. But the program wasn’t sustained. Funding dried up, surveillance stopped, and yaws resurged in areas where transmission hadn’t actually been eliminated. By the 1990s, it was clear the disease persisted in residual foci.
The 2012 relaunch marked a renewed commitment. WHO established the Eradication of Yaws Programme with a target of eradicating yaws by 2020. That deadline passed unmet. The current target, embedded in WHO’s 2021-2030 Roadmap on Neglected Tropical Diseases (https://www.who.int/teams/control-of-neglected-tropical-diseases/overview/roadmaps/eradication-of-yaws), is eradication by 2030. Is this realistic?
Progress has been mixed. According to WHO’s 2023 progress report on neglected tropical diseases, several countries have achieved or are close to achieving elimination. India certified elimination in 2016—the first country to do so under the renewed strategy. Ecuador achieved elimination in 2022. Several Pacific island nations are progressing toward certification. But the countries with highest burden—Papua New Guinea particularly—face persistent challenges.
Papua New Guinea’s experience illustrates the obstacles. The country has conducted multiple rounds of MDA in high-prevalence provinces, achieving substantial prevalence reduction in targeted areas. But rugged geography, limited road infrastructure, political instability, and competing health priorities have prevented comprehensive coverage. According to research published in The Lancet Global Health (https://www.thelancet.com/journals/langlo/article/PIIS2214-109X(18)30415-7/fulltext), prevalence remains above 5% in several provinces despite treatment campaigns, suggesting sustained transmission persists.
Funding remains chronically inadequate. Pfizer’s donation of azithromycin through the International Trachoma Initiative provides treatment, but operational costs—surveillance, health worker training, community mobilization, transportation to remote areas—require sustainable financing. WHO estimates eradication would cost approximately $100-150 million over 10 years—trivial compared to global health budgets, but endemic countries can’t finance this alone and donor commitments have been insufficient.
Partnership coordination is improving but incomplete. WHO collaborates with national ministries of health, CDC, several academic institutions, and NGOs including the International Trachoma Initiative and Médecins Sans Frontières. But coordination is ad hoc rather than through a dedicated eradication program with clear governance, adequate financing, and political backing at the highest levels. Compare this to polio eradication—a standing global program with billions in funding, head-of-state political commitment, and coordination mechanisms that mobilize resources rapidly. Yaws has none of that infrastructure.
The editorial question is whether the world will finish the job. Yaws eradication is technically feasible—we have a cheap, effective treatment and no biological barriers to interrupting transmission. We’re 90% of the way there; only 13 countries remain endemic. Yet we’ve stalled. Why? The answer is brutally simple: the populations still affected by yaws have no political power. They live in remote, impoverished communities in low-income countries. They don’t vote in elections that determine global health budgets. Their suffering generates no media attention, no advocacy campaigns, no celebrity endorsements. From world history to contemporary global health policy, we’ve seen this pattern repeatedly: diseases affecting the poorest and most marginalized persist long after technical solutions exist because global health priorities reflect global power structures.
Will 2030 be different from 2020? Unless something changes—sustained financing, political commitment at national and international levels, health system strengthening in endemic countries—the answer is no. We’ll continue to see progress reports documenting incremental advances, countries achieving elimination one by one, prevalence declining slowly. And in the meantime, tens of thousands of children will develop disfiguring, disabling lesions from a disease we could eliminate for the cost of what wealthy countries spend on a single military aircraft. That we choose not to reveals more about global priorities than any policy document could. Similar to sustained campaigns that have driven progress on other health issues, as demonstrated by initiatives like World Cancer Day awareness efforts, yaws eradication requires not just technical capacity but sustained political will—and that remains the missing ingredient.
FAQ
What is yaws and how is it transmitted?
WHO defines yaws as a chronic bacterial infection caused by Treponema pallidum subspecies pertenue, closely related to syphilis but transmitted through skin-to-skin contact rather than sexual contact. Transmission occurs when direct contact between infectious skin lesions on an infected person and broken skin (cuts, abrasions) on a susceptible individual allows bacteria to enter. Children aged 5-15 in impoverished tropical communities are most affected.
How many countries still have yaws and where are they?
WHO reports that 13 countries remain endemic for yaws as of 2024: Papua New Guinea, Solomon Islands, Vanuatu, Ghana, Cameroon, Central African Republic, Republic of Congo, Côte d’Ivoire, Democratic Republic of the Congo, Indonesia, Liberia, Togo, and Benin. Papua New Guinea carries the highest burden. Over 80 countries eliminated yaws since the 1950s through mass treatment campaigns.
Is yaws curable and what is the treatment?
Yes, yaws is curable. WHO reports a single oral dose of azithromycin (30 mg/kg for children, 2 grams for adults) achieves cure rates exceeding 95%. This simple treatment heals active lesions within weeks and prevents progression to late-stage disease. Previous treatment used intramuscular penicillin, but azithromycin’s oral formulation enables mass drug administration by community health workers.
What are the symptoms and complications of untreated yaws?
WHO identifies three stages: primary (painless skin papule becoming raspberry-like lesion), secondary (multiple skin lesions, painful foot papillomas making walking difficult, bone pain), and tertiary (occurring in 10% of untreated cases—destructive bone deformities, facial disfigurement, chronic disability). Unlike syphilis, yaws doesn’t affect heart or nervous system, but skeletal and tissue destruction causes permanent disability including inability to walk normally.
Why hasn’t yaws been eradicated despite having an effective treatment?
WHO’s eradication target for 2030 faces challenges including: geographic isolation of endemic communities requiring expensive logistics to deliver treatment, inadequate sustained financing (estimated $100-150 million needed over 10 years), health system weaknesses in endemic countries, competing health priorities, and insufficient political commitment. The 1950s-60s campaign reduced prevalence by 95% but wasn’t sustained, allowing resurgence. Current efforts face similar sustainability challenges.
Sources
- World Health Organization. (2024). Yaws. Retrieved from https://www.who.int/health-topics/yaws
- World Health Organization. (2021). Ending the neglect to attain the Sustainable Development Goals: A road map for neglected tropical diseases 2021–2030. Retrieved from https://www.who.int/publications/i/item/9789240010352
- Mitjà , O., et al. (2013). Mass treatment with single-dose azithromycin for yaws. New England Journal of Medicine, 372(8), 703-710.
- Marks, M., et al. (2015). Challenges and key research questions for yaws eradication. The Lancet Infectious Diseases, 15(10), 1220-1225.
DISCLAIMER
This article adapts publicly available information from WHO’s Yaws page. This content is for informational and educational purposes only and does not constitute medical advice. ObserverVoice.com is a news and information platform—not a healthcare provider.
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