What Was the Black Plague?
3. Causes
The plague is caused by a bacterium known as Yersinia pestis. The bacterium can infect a range of animals, including humans. These include animals that will often be found around human towns and cities, such as mice and rats. These animals will typically have fleas and, when these fleas feed on an animal, they too can become infected.
After a flea has become infected it may then go on to try and feed on a person, potentially passing on the bacterium. It is also possible to become infected after being in contact with the blood of an infected animal. Another variety of the plague, the pneumonic plague, is transmitted through infected droplets when an infected person coughs or sneezes.
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