Causes of plague
Learn about the causes of plague, how it is spread and where it is found.
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The cause of plague
Plague is a disease caused by the Yersinia pestis bacterium. This disease can affect both animals and humans.
How plague is spread
You can become infected with plague from:
- the bite of a flea infected with the plague
- direct contact with infectious tissues or fluids while handling an animal or human that is sick with or has died from plague
- breathing in droplets coughed or sneezed from the lungs of an animal or human with pneumonic plague
Where plague is found
Plague bacteria can be found in small animals such as:
- rats
- ground squirrels
- other rodents and their fleas
It is found on all continents except Oceania.
Historically, outbreaks of human plague have occurred in:
- Asia
- Africa
- Europe
- North America
- South America
Since the 1990s, most human cases have occurred in Africa.
Plague is most common in the following countries:
- Democratic Republic of Congo
- Madagascar
- Peru
In North America, people are rarely infected with plague. About 7 cases of plague occur each year in the southwestern United States. Human to human transmission of the plague has not been confirmed in the U.S. since 1925.
In Canada, human cases of plague are very uncommon. The last case was reported in 1939.
It has been absent from Europe for over half a century.