Contagious tropical disease, caused by a variant of the spirochete that causes syphilis. Yaws spreads mainly by discharge from skin sores, not sexual activity. It is common in children, who usually become immune. In the first stage, a skin sore starts as a wartlike thickening, cracks open, leaks fluid, and bleeds easily. A month or more later, multiple sores erupt. The third stage (much rarer than in syphilis) involves destruction of skin, mucous membranes, and bones. Penicillin cures early-stage yaws. Prevention requires isolation and prompt treatment and personal and group hygiene.
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