Causes

The plague bacteria, Yersinia pestis, is transmitted to humans through the bites of fleas that have previously fed on infected animals, such as:

• Rats
• Mice
• Squirrels
• Rabbits
• Prairie dogs
• Chipmunks
• Voles

The bacteria can also enter your body if a break in your skin comes into contact with an infected animal's blood. Domestic cats and dogs can become infected with plague from flea bites or from eating infected rodents.

Pneumonic plague, which affects the lungs, is spread by inhaling infectious droplets coughed into the air by a sick animal or person.