大流行的严重程度可以随着时间的推移而发生变化，而且可能会因地点或人群而异。

The severity of pandemics can change over time and differ by location or population.

youdao

大流行的严重程度可以随着时间的推移而发生变化，而且可能会因地点或人群而异。

The severity of pandemics can change over time and differ by location or population.

youdao