It is not known what caused their sudden spread, but experts have theorized that an increase in global travel and the banning of certain pesticides may be partly responsible.

至今它们大肆传播的确切原因不得而知，但专家表示，可能的因素包括全球旅行的增加和某些杀虫剂的禁用。

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They also partly suppress the body's own immune reaction to any cancer growths, making the cancer more prone to spread.

这些药物也有一定的抑制人体自身抑制癌症生长免疫反应，使癌细胞更容易扩散。

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That is partly because fire can spread, and your neighbours should not suffer for your carelessness.

部分原因是，火势可能会蔓延，你的邻居不应因为你的粗心而遭受损失。

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But with the revolution of democracy in Athens, which also spread then to other Greek cities, partly because Athens did what George Bush tried to do in Iraq, they tried to force democracy on other Greek cities around the Eastern Mediterranean also.

但随着雅典民主革命的进行，这场革命随后传到了其他希腊城市，原因之一，类似小布什在伊拉克的计划，雅典企图把民主制度,推行到地中海东部的其他希腊城市。

耶鲁公开课 - 新约课程节选

That is partly because some Americans fear the violence is starting to spread northward, although such worries look exaggerated (see article).

ECONOMIST: Mexico and the United States

Numbers of livestock have fallen by 40%, partly thanks to an epidemic of screw worms that had spread to two-thirds of Iraq's provinces by the end of last year.

ECONOMIST: Iraq

Inflation targeting spread around the world rapidly during the 1990s and 2000s, partly due to the influence of the academic work of Mr. Bernanke and his co-authors.

FORBES: Should Bernanke Focus Only on Inflation?