Plague is caused by the bacteria
Yersinia pestis
. Rodents, such as rats, carry the disease, which is spread by fleas.
In the Middle Ages in Europe, massive plague epidemics killed millions of people. These days, plague occurs sporadically but can be treated and usually cured if caught early. Plague can still be found on nearly all continents. Most human cases have occurred in Africa.
Today, plague is rare in the United States. An average of about 7 cases occur every year. Plague was introduced in the 1900s by rats aboard steamships. It caused epidemics in many urban areas up until 1925. The disease spread to the rural rodent population in the Western United States. Now most cases of plague occur in rural areas primarily in these states:
- Northern New Mexico and Arizona, and southern Colorado
- California, southern Oregon, and western Nevada
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Wild animals affected by plague include:
- Squirrels
- Rats
- Prairie dogs
- Chipmunks
- Mice
- Voles
- Rabbits
- Marmots
Animals that eat other animals can get the disease by eating infected prey. Domestic animals, such as dogs and cats can contract plague if they are bitten by fleas that carry the disease or eat small rodents such as mice.
People can get plague in the following ways:
- Being bitten by a flea
that carries the plague bacteria from an infected animal. Dogs and cats can also carry infected fleas into the home and spread the disease.
- Handling an infected animal
and coming into contact with body fluid or tissue.? For example, hunters who skin and prepare an infected animal could become infected.
- Breathing in respiratory droplets
from an infected human or animal. Plague lung infection is called pneumonic plague. When someone with pneumonic plague coughs, tiny droplets carrying the bacteria move through the air. Anyone who breathes in these particles may catch the disease. In the United States, there have been cases of owners becoming infected by their sick cat through respiratory droplets.