In some cases, control, especially self-control, is necessary.

在某些情况下，控制，尤其是自我控制是必要的。

Case control and cohort studies are two of the ways epidemiologists can help identify the cause of the outbreak.

病例对照和队列研究是流行病学家可以帮助确定爆发原因的两种方法。

And the way you find out is do careful following and natural history studies and case control studies.

你发现的方法是仔细跟踪和自然历史研究以及病例对照研究。