Yaws is a chronic illness that first affects the skin, and later the bones.

Yaws tends to strike children, particularly between the ages of two and five. It is common in areas where poverty and overcrowding interfere with good hygiene. It is most prevalent in rural areas throughout Africa, Southeast Asia, and in locations bordering the equator in the Americas.

Yaws is caused by a spiral-shaped bacterium (spirochete) called Treponema pertenue. This bacterium belongs to the same family as the bacterium that causes syphilis.

Yaws is passed among people by direct skin contact. The bacterium requires a scratch or insect bite to actually settle in and cause infection. An injury on the leg is the most common part of the body through which the bacteria enter. Young children, who are constantly bumping themselves in play, who wear little clothing, who do not wash their hands often, and who...