In different times of history why have infectious disease epidemics appeared suddenly, killed many people, then faded out?

maybe because everybody who eventually got the disease died and the disease died with the people

Explanation:

Well they only last for a certain amount of times. Or they are only around for certain seasons on are only in certain areas. Like the flu you normally only see people get it during the winter, that's when it is at it's strongest. They start to fade out because people slowly start to build immunity on them or start to develop different ways to protect themselves.

Explanation:

Hope I helped:)

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