Definition of Yaws:

Yaws is a chronic infection caused by the bacteria Treponema pertenue, which primarily affects the skin, bones, and joints.

Causes, incidence, and risk factors:

Yaws is an infection caused by the spiral-shaped bacterium (spirochete) called Treponema pertenue. It is closely related to the organism that causes syphilis, but this disease is not sexually transmitted. Yaws mainly affects children in rural, warm, tropical areas -- primarily Caribbean Islands, Latin America, West Africa, India, and Southeast Asia.

Yaws is transmitted by direct contact with skin lesions of infected people. Approximately two to four weeks after infection, the child develops a sore "mother yaw" where the organism entered the skin.

The sore appears as a "raspberry-like" growth or group of papules at the site of infection and is usually painless. These lesions may persist for months. Additional satellite lesions may appear shortly before or after the mother yaw heals. Children may also develop inflammation of the bones and fingers.

The final stage involves destructive lesions of the skin and bones which can lead to severe disfigurement and disability. It occurs in up to 20% of untreated individuals.