24/7 Tempo has compiled a list of the 20 worst epidemics and pandemics in history. An epidemic is defined as the widespread occurrence of an infectious disease in a community at a particular time.

Outbreaks of disease have impacted the lives of individuals and communities throughout history. Whether it's an epidemic (a somewhat localized influx of cases) or a pandemic (a global phenomenon ...

Some of the biggest pandemics in history include the bubonic plague, cholera and smallpox ... The 1918-1920 outbreak was the worst pandemic in history, killing 50 to 100 million people.

AI may make human-caused pandemics 5× more likely than last year, experts warn in a study shared exclusively with TIME.