Yaws is a long-term (chronic) infection that mainly affects the skin, bones, and joints.
Causes, incidence, and risk factors
Yaws is an infection caused by the spiral-shaped bacteria, Treponema pallidum, subspecies pertenue. It is closely related to the bacterium that causes syphilis, but this disease is not sexually transmitted. Yaws mainly affects children in rural, warm, tropical areas, such as the Caribbean Islands, Latin America, West Africa, India, and Southeast Asia.
Yaws is transmitted by direct contact with the skin sores of infected people.
About 2 - 4 weeks after infection, the person develops a sore called a "mother yaw" where bacteria entered the skin. The sore is a growth that may be tan or reddish and looks like a raspberry. It is usually painless but does cause itching.
These sores may last for months. More sores may appear shortly before or after the mother yaw heals as the person scratches or spreads the bacteria from the mother yaw to uninfected skin. Eventually the skin sores heal.
Other symptoms include:
Scarring of the skin
Swelling of the bones and fingers
In the advanced stage, sores on the skin and bones can lead to severe disfigurement and disability. This occurs in up to 1 in 5 people who do not get antibiotic treatment.
Signs and tests
A sample from a skin sore is examined under a special type of microscope (darkfield examination).
There is no blood test for yaws. However, the blood test for syphilis is usually positive in people with yaws because the bacteria that cause these two conditions are closely related.
Treatment involves a single dose of one type of penicillin, or 3 weekly doses for later stage disease. It is rare for the disease to return.
Anyone who lives in the same house with someone who is infected should be examined for yaws and treated if they are infected.
If treated in its early stages, yaws can be cured. Skin lesions may take several months to heal.
By its late stage, yaws may have already caused damage to the skin and bones. It may not be fully reversible, even with treatment.
Yaws may damage the skin and bones, affecting the appearance and ability to move. It can also cause deformities of the legs, nose, palate, and upper jaw.
Calling your health care provider
Contact your health care provider if you or your child has sores on the skin or bone that don't go away, and you have stayed in tropical areas where yaws is known to occur.
Widespread campaigns in the 1950s and 1960s to wipe out yaws through penicillin treatment have dramatically decreased the number of cases worldwide.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.