他们是非常可能接触到病毒，并而且非常可能流传病毒的一类群体。
They are the people who will be most likely to be coming into contact with the virus and the ones who could be passing it on.
一种新的流感病毒在四处流传。
研究团队结论认为，这种病毒在人类感染的首例之前，已经神不知鬼不觉地在猪只身上流传演化已久。
This, they conclude, means the bug was circulating and evolving undetected in swine for quite some time before the first people were infected.
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