Plague is caused by the rod-shaped bacteria Yersinia pestis. Y. pestis can make us sick in different ways, depending on how the bacteria invade our body. When it’s transmitted through contact with animals (typically a flea that recently fed on another infected animal), the bacteria tend to make their way to our lymph nodes and cause bubonic plague.

Plague bacteria can also be inhaled into the lungs, causing pneumonic plague.

And seldomly, it can reach the bloodstream, causing septicemic plague.

Though plague was once one of the deadliest infectious diseases of humankind, causing pandemics like the Black Death, it’s much rarer these days and more easily managed with antibiotics when it does show up. But plague bacteria still circulate among wildlife, especially rodents, meaning that human infections can and do occasionally appear.

The person likely caught it from their pet cat, who recently became very ill and developed an abscess (a pocket of pus, usually indicative of infection) that had to be drained.

Cats are known to be especially vulnerable to plague, often catching it from wild rodents or their fleas.