Illness finds its way in by the mouth.

病从口入.

《现代汉英综合大词典》

HYGIENE TEACHER: How can you prevent disease caused by biting insects?

卫生老师: 怎样才能防止病从口入?

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Diseases enter by the mouth; misfortunes issue from it.

病从口入, 祸从口出.

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One must wash his hands before meals to avoid diseases.

为了避免病从口入,饭前要净手.

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Chinese has a saying all diseases enter through the mouth , so I began by eating well.

俗话说“病从口入”, 所以我就先从吃开始.

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