xiǎo / ér / má / bì / zhèng / céng / jīng / shì / wēi / hài / ér / tóng / jiàn / kāng / de / yán / zhòng / jí / bìng

小儿麻痹症曾经是危害儿童健康的严重疾病。

Poliomyelitis was once a serious disease that threatened children's health.