It spreads quickly once tiny beads of fluid enter your body, often from a sneeze, cough, or kiss. There are hundreds of viruses that can cause a cold; you can never build up immunity to all of them.

一旦侵入身体一丁点含病毒的液体，病毒就会快速蔓延开来，常常一个喷嚏、一个咳嗽或一个亲吻就足以致病，因为导致感冒的病毒有成百上千种，所以身体无法对所有病毒都产生免疫。

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Unlike the avian virus, the new H1N1 virus spreads very easily from person to person, spreads rapidly within a country once it establishes itself, and is spreading rapidly to new countries.

不像禽流感，新的H1N1病毒更容易在人与人之间传染，一旦在一个国家出现，它就能迅速蔓延全国，并且向未发现这种病毒的国家蔓延的速度也非常快。

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Almost nothing works against melanoma once it spreads beyond the skin.

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Others think that people will use the public system once word spreads that it offers good, free care.

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The bone is one of the most common places where breast cancer spreads, and once it does so it is not considered curable.

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