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Which rodents can carry plague bacteria?

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two plague victims with sores lying in bed, while a robed figure gestures above them. — plague Image depicting victims of the sixth biblical plague.

Plague is primarily a disease of rodents, which serve as the natural reservoir for the bacterium Yersinia pestis. While the disease is enzootic—meaning it is constantly present in animal communities—it can reach epizootic proportions, causing widespread death among rodent populations.12

Various wild and domestic rodents can carry the bacteria, including:

Black rats (Rattus rattus)1
Great gerbils (Rhombomys opimus)1
Ground squirrels1

The transmission cycle typically involves fleas that feed on these infected rodents. When an epizootic outbreak kills the rodent hosts, the fleas may seek out humans, leading to potential infection. While rodents are the primary carriers, humans can also be exposed through direct contact with the tissues or bodily fluids of other infected animals, such as domestic cats. Because it is impossible to eliminate rodents from the wild, the disease remains present in nature, and human cases are best controlled by limiting exposure to these infested animals.13