Smallpox has anti-static function, so the surface is not contaminated with dust, just regular nursing with water to wipe light (usually once a month).

天花本身具有防静电功能，所以其表面是不会沾染尘埃，护理只需定期用清水轻抺即可（一般每月一次）。

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It should be noted that a once-worn respirator will also be contaminated on its inner surface by the microorganisms present in the exhaled air and oral secretions of the wearer.

需要注意的是，佩戴过一次的呼吸器的内表面也会被佩戴者呼出的空气及唾液中的微生物所污染。

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"Current technologies are insufficient to prevent food-borne illness," he said. "in the present system, once produce is contaminated with something like E." coli, that's it.

当前技术对于预防食源性疾病是不够的，一旦农产品被大肠杆菌等病原体污染，将很可能会导致疾病发生。

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But he says that once contaminated peanut butter is consumed, the bacteria can multiply quickly and make people sick.

CNN: Kellogg to recall products over salmonella concerns

The federal government and the egg industry agree that about one in 20, 000 eggs is actually contaminated: a figure that would put the average egg-eater at risk only once every 50 years.

ECONOMIST: Food safety: No sunny side up | The