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Last updated: 4/17/2025
Years published: 1986, 1994, 2003, 2005, 2009, 2024, 2025
NORD gratefully acknowledges Gioconda Alyea, MD (FMG), MS, National Organization for Rare Disorders, for assistance in the preparation of this report.
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Yaws is a long-lasting (chronic), sometimes disfiguring and disabling infection that mostly affects children living in warm, tropical areas. It’s caused by a type of bacteria and only affects humans.
Yaws spread through direct skin contact with someone who has the infection. It’s not considered a sexually transmitted disease.
The bacteria that cause yaws are part of a group called endemic treponematoses. These are spiral-shaped bacteria also responsible for other infections like bejel (endemic syphilis) and pinta. Among these, yaws is the most common. A different kind of Treponema bacteria causes syphilis, a sexually transmitted infection, which is more common but different from yaws.
Yaws mainly affect people who live in poor, rural communities in hot, humid, tropical forest regions, like parts of Africa, Asia, Latin America and the Pacific. Poor living conditions, limited access to healthcare and poor hygiene make it easier for the disease to spread.
The infection usually starts with a wart-like bump (called a papilloma) that’s full of bacteria. If untreated, it can break open into an ulcer. In later stages, children may develop raised yellow skin lesions or pain in the long bones, especially in the arms and legs (a condition called dactylitis). These skin lesions are highly contagious and without treatment, the infection can spread quickly to others.
Although yaws is still common in tropical countries, it has not been found in the United States.
Yaws can be cured with a single dose of an antibiotic called azithromycin taken by mouth.
The incubation period, the time from the exposure to the bacteria that causes the disease, and the onset of the symptoms is 9–90 days, with an average of 21 days. Humans are the only source of infection. Yaws signs and symptoms typically present in two stages:1,2,3
In between primary and secondary or secondary and tertiary stages, a latent period occurs where serologic exams are positive but where there are no signs and symptoms.1,3
Yaws is part of the endemic treponematoses, a group of chronic bacterial infections caused by treponemes, spiral-shaped bacteria, that are closely related to the bacteria that cause syphilis.
The endemic treponematoses include yaws, caused by Treponema pallidum subsp. pertenue, bejel (caused by T. pallidum subsp. endemicum) and pinta (caused by T. carateum).1,3,4
In addition, both yaws and syphilis are caused by bacteria belonging to the Treponema pallidum species. Syphilis is caused by Treponema pallidum subspecies pallidum.
T. pallidum belongs to a family of gram-negative spiral-shaped bacteria, the Spirochaetaceae,and has a length ranging from 10 to 15 microns and a diameter of 0.2 microns, making it invisible to light microscopy except under dark field illumination. Electron microscope studies have shown that there are not significant differences in shape or structure between T. pallidum subspeciesor with T. carateum.3
Treponemes penetrate the human host through epidermal micro-scrapes, adhere to the skin cells and multiply locally. After invasion, the organisms appear in lymph nodes within minutes and disseminate widely within hours, reaching and surviving in distant skin and organs.
New yaws skin lesions are rarely found in adults, suggesting that people might develop some kind of resistance to getting infected with yaws again after they’ve had it once, which means their body might be able to fight off the infection if exposed to it again.
Yaws is usually transmitted by direct contact with the infected skin sores of affected individuals. In some people, yaws may be transmitted through the bite of an infected insect.1,3,4
A whole genome analysis of a limited number of T. p. pallidum, T. p. pertenue, and T. p. endemicum have shown that the overall genetic similarity between the three subspecies is very high (99.8%), meaning they are closely related. However, there are specific regions in the DNA where the sequences differ, and these regions are used to tell the different subspecies apart. These genetic differences allow for the development of tests that can identify and distinguish between syphilis and yaws strains, which is not possible with other tests.3
It’s currently unknown whether these small genetic differences are directly linked to the distinct symptoms associated with syphilis and yaws.
Yaws is a common infectious disease among children living in the tropical areas of Africa, South and Central America, the West Indies and the Far East. It is not found in the United States. Yaws mainly affects children under 15 years of age (with a peak between 6 and 10 years) and affects females and males equally.1,2,3
The prevalence of yaws declined greatly following a mass treatment campaign with penicillin by the World Health Organization (WHO) in the 1950s and ’60s. However, there has been a resurgence of yaws in certain countries in Africa and Southeast Asia.
WHO categorizes countries into three groups based on yaws endemicity:4,5
As of 2023, 16 countries were considered endemic for yaws, and 82 countries, areas and territories were considered previously endemic, with current status unknown.3 The status of yaws endemicity can be seen at the WHO website, World Health Observatory.
In the United States, only three cases of yaws were reported between 1921 and 1923.6
Yaws is usually suspected by doctors based on the signs and symptoms and where the person lives or has been.1,3
To confirm yaws, doctors usually rely on certain blood tests known as serology. Blood tests (serology) are tests that check for antibodies proteins that the immune system makes. Blood tests for yaws are the same ones used to test for syphilis, because the bacteria are very closely related. There are two kinds of blood tests and both are needed to make a diagnosis:3
Nontreponemal tests: These tests check for general signs of any treponemal infection. Two common tests are RPR (rapid plasma reagin) and VDRL (venereal disease research laboratory). These tests measure how active the infection is and they can help track whether treatment is working, as the results usually improve as the infection clears.
Because these tests are not specific for treponema, these tests can sometimes give false positives (tests are positive but the person does not have the infection) in people affected with other conditions, including malaria, leprosy and rheumatologic diseases.
In the early stages of infection, the test might come back negative, so doctors may repeat the test in 2–4 weeks or use another method like PCR (see below) if needed.
Treponemal tests: Treponemal tests (Treponema pallidum hemagglutination assay (TPHA), Treponema pallidum particle agglutination assay (TPPA), the fluorescent treponemal antibody absorption (FTA-Abs), Treponemal enzyme immunoassay and Treponemal chemiluminescent immunoassay) are more specific than non-treponemal tests. These tests look for antibodies that target the bacteria Treponema but do not differentiate among the different subtypes (subspecies) of Treponema as all these diseases including syphilis, yaws, pinta, and bejel, are caused by subspecies of Treponema pallidum:
These assays cannot distinguish between current (untreated) and previously treated infection and remain positive even after successful treatment.
Treponemal tests detect antibodies that react with T. pallidum antigens, but those antigens are shared across these subspecies. So, a positive test means the person has or had a treponemal infection, but not which one.
Once a person tests positive, this person may stay positive for life, even after the infection is gone.3
There are also quick tests that can be done on the spot, without sending samples to a lab. These are especially useful in rural or remote areas. These are called rapid tests (point-of-care tests). They detect treponemal antibodies (the specific ones linked to yaws) and they don’t need special equipment or electricity. Some versions test for both types of antibodies at once (treponemal and nontreponemal) like the DPP (dual path platform) test. They work very well when the infection is active, and antibody levels are high. They’re less accurate when the infection is mild or early.3
A PCR (polymerase chain reaction) test is a molecular test that looks directly for the DNA of the bacteria that causes yaws. To do this test a doctor swabs the fluid from a skin sore. The lab tests the sample to see if the bacteria’s genetic material is present. PCR testing provides definitive confirmation of yaws by detecting the DNA of Treponema pallidum pertenue directly from skin lesions.3
The PCR confirms early infections before antibodies show up in blood and can tell the difference between yaws and other infections that cause similar sores.3
PCR is very accurate but it’s usually only available in research labs or specialized hospitals, not in most clinics or rural areas.3
If yaws affect the bones, doctors may order an X-ray to look for signs of bone damage. This happens in more advanced cases.1,3
Treatment
Yaws can be cured with one of two antibiotics:¹˒³
People who receive treatment should return for a follow-up checkup 4 weeks later. At that point, more than 95% of people show full healing.⁴ If the infection doesn’t go away, doctors may test for antibiotic resistance. In those people, treatment with benzathine penicillin is recommended.⁵
There is no vaccine for yaws. Preventing it depends on good hygiene and health education to stop the spread. Also, anyone who has been in close contact with a person who has yaws should receive preventive treatment with antibiotics just in case.¹
To stop yaws in communities, the recommended strategy is called “total community treatment (TCT)”. This means giving azithromycin (30 mg/kg, max 2 g) to at least 90% of people in areas where yaws is present.¹˒⁵
To officially say that yaws has been eradicated from an area, the following conditions must be met:⁵
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Toll free: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]
Some current clinical trials also are posted on the following page on the NORD website: https://rarediseases.org/living-with-a-rare-disease/find-clinical-trials/
For information about clinical trials sponsored by private sources, contact: www.centerwatch.com
For information about clinical trials conducted in Europe, contact: https://www.clinicaltrialsregister.eu/
1. Maxfield L, Corley JE, Crane JS. Yaws. [Updated 2023 Jul 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK526013/ Accessed April 17, 2025.
2. Yaws. MedlinePlus. Updated:12/31/2023. https://medlineplus.gov/ency/article/001341.htm Accessed April 17, 2025.
3. Mitjà O & Mabey D. Yaws, Bejel and Pinta. UpToDate. Feb 27, 2024. https://www.uptodate.com/contents/yaws-bejel-and-pinta Accessed April 17, 2025.
4. Yaws (Endemic treponematoses). World Health Organization. Available from: https://www.who.int/health-topics/yaws#tab=tab_1 Accessed April 17, 2025.
5. Yaws. World Health Organization. 12 January 2023. Available from: https://www.who.int/news-room/fact-sheets/detail/yaws Accessed April 17, 2025.
6. Zoni AC, Saboyá-Díaz MI, Castellanos LG, Nicholls RS, Blaya-Novakova V. Epidemiological situation of yaws in the Americas: A systematic review in the context of a regional elimination goal. PLoS Negl Trop Dis. 2019;13(2):e0007125. Published 2019 Feb 25. doi:10.1371/journal.pntd.0007125
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