Yaws is a tropical disease of the skin. It is caused by a germ (a bacterium) very close to the one that causes syphilis, but yaws is NOT a sexual disease — it spreads by ordinary skin touching skin, so children catch it from other children while playing. It starts as one bump or sore, often on the leg. That first sore heals, but months or years later more sores come out over the body, and in bad cases the disease eats into the bones and the face and leaves the person changed for life. It is found in hot, wet, poor places — parts of West Africa, Southeast Asia, and the Pacific islands. Penicillin cures it easily, and health workers have almost wiped it out; it comes back where clean water and doctors are far away. Note the shape of the word: it ends in -s but it is one disease, not many things. People say 'yaws is a disease' — the verb is singular, like 'news is'. You will meet this word in medicine, in history books, and in stories about tropical travel, almost never in daily talk.

雅司病（熱帶皮膚病，又稱印度痘）