This is why many viruses, such as measles, make us ill only once.

这就是为什么许多病毒，如麻疹，只会使我们生病一次。

youdao

This is why many viruses, such as measles, make us ill only once.

这就是为什么许多病毒，如麻疹，只会使我们生病一次。

youdao