A virus presently located in a remote rain forest could, by means of air travel, be in a major city by this time tomorrow. We now live in such crowded cities that the scope for transmission of a virus which travels through air is greater than ever

A virus presently located in a remote rain forest could, by means of air travel, be in a major city by this time tomorrow. We now live in such crowded cities that the scope for transmission of a virus which travels through air is greater than ever before.

我们现在生活的城市人口这么拥挤，病毒在空气中传播的范围比以往任何时候都要大的多。