Modeling shows plague spread from human to human, not rat to human as previously believed

Plague is responsible for killing millions of humans from the 14th through 19th centuries. Scientists originally thought the pandemics were caused when people were bit by fleas that had previously been feeding off of rats infected with the plague causing bacteria, Yersinia pestis. However, research published in the Proceedings of the National Academy of Science suggests the pandemics were caused by human ectoparasites meaning fleas and lice were spreading plague causing bacteria from human to human not rat to human.

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