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Someone in Wyoming Caught the Plague From Their Cats

Plague is rare in the U.S., but wild animals and free-roaming pets—and their fleas—can still carry the bacteria and infect us.

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A Wyoming resident appears to have caught a serious case of the plague from their own cats, health officials reported this week. The woman contracted pneumonic plague, a rare form of the already very rare disease. Though the risk of plague in the U.S. and in Wyoming is generally very low, officials have notified others who may have been exposed and could need antibiotic treatment, since pneumonic plague can be spread from person to person.

Plague is a bacterial disease that comes in several different flavors, depending on how the bacteria (Yersinia pestis) infects the body. Most cases are known as bubonic plague and are typically caused by contact, including bites, with infected animals (usually small mammals) or the fleas they carry. In this form, the bacteria invades the lymph nodes. If the bacteria ends up in the respiratory tract, it leads to pneumonic plague, which can cause pneumonia and flu-like symptoms, including a contagious cough. This can happen when plague bacteria spreads to the lungs or when a new victim breathes in infected droplets from someone else with pneumonic plague. Lastly, there’s septicemic plague, which is when the bacteria reach the blood. This can happen from an animal or flea exposure, too, but is often the result of untreated bubonic plague.


Plague, as the name suggests, used to be one of the worst menaces of humanity and is responsible for some of the deadliest epidemics in history, including the Black Death. But better sanitation and the emergence of antibiotics have made plague a lot less common and dangerous in most places of the world. Even in the U.S., though, there are still natural animal hosts of the bacteria, and cases do occasionally spill over to people.

Cases in the U.S. tend to involve exposure to wildlife or their fleas, but free-roaming pets, including cats, are known to sometimes catch the infection and then pass it on to their owners. And that seems to be what occurred here, according to the Wyoming Department of Health. On Wednesday, they announced that a northern Fremont County resident developed a rare case of pneumonic plague, likely through contact with “sick pet cats.”


Courtney Tillman, an epidemiologist with the health department, told Gizmodo in an email that the victim is a woman who is currently experiencing serious illness.

Plague, no matter the form, should be treated as soon as possible. But pneumonic plague is especially worrying, both due to the rapid course of illness (it can become fatal within a day of symptoms starting) and because it’s the only form that can be contagious to others. People exposed to plague are typically given antibiotics as a prophylactic treatment, and health officials say they’re reaching out to anyone suspected of having come into contact with the woman during the window of transmission. So far, though, only one case has been identified.

Again, plague is very rare in the U.S. In 2019 and 2018, according to the Centers for Disease Control and Prevention, there was a single case reported each year. This is only the seventh case reported in Wyoming since 1978, though some of those were actually caught out of state. Still, health officials do note that there are common-sense ways to stay as safe as can be from this historic disease.

“It’s safe to assume that the risk for plague exists all around our state,” said Alexia Harrist, state health officer and epidemiologist with the health department, in a statement Wednesday. “While the disease is rare in humans, it is important for people to take precautions to reduce exposure and to seek prompt medical care if symptoms consistent with plague develop.”


These precautions include keeping your homes and yards clean to avoid rat infestations; wearing flea repellent during outdoor activities like hiking; always wearing gloves when touching potentially infected animals (or simply not touching them at all); and not sleeping with cats and dogs that are allowed to roam freely outdoors, especially if they seem sick.

This article has been updated with further information provided by the Wyoming Department of Health.