• An average of five plague cases are reported in the U.S. annually, mostly in New Mexico and Arizona.
• Two cases reported in recent years occurred in patients exposed to Yersinia pestis through sick cats.

Cases of plague are rare but not unheard of in the United States. Cases of pneumonic plague, the type at the center of a mysterious story in Russia, are even rarer.

The death of a man from pneumonic plague last year in Arizona was linked to contact with sick cats, according to a recently published report in MMWR.

“Pneumonic plague is a rare and serious form of plague caused by Yersinia pestis,” the flea-borne bacterium that causes the disease, Grace Marx, MD, medical officer in the CDC’s Division of Vector-Borne Diseases, told Healio.

“It develops when bacteria spread to the lungs of a patient with untreated bubonic or septicemic plague (secondary pneumonic plague), or when a person inhales infectious droplets coughed out by a person or animal with pneumonic plague (primary pneumonic plague),” she said.

Marx noted that pneumonic plague is “the most serious form of the disease” and is the only form of plague that can spread from person to person.

According to the CDC, there is an average of five human plague cases reported in the U.S. each year, mostly in Arizona and New Mexico, although the average can fluctuate greatly. Zero cases were reported in 2022 compared with 16 cases in 2015, for example. The majority of cases — more than 80% — are bubonic plague. A 2015 CDC study showed that pneumonic plague accounted for just 74 cases between 1900 and 2012, and only a handful more since.

Wang explained that cats are a recognized cause of human plague cases, citing a Clinical Infectious Diseases paper that reported 23 cases of cat-associated human plague — five of which were primary pneumonic plague — in eight states between 1977 and 1998 alone. Many of these exposures occurred when people were caring for a sick cat, she said.

Marx and colleagues authored the MMWR report about the Arizona case, which began with a description of a young adult man being evaluated after 2 days of abdominal pain, chest pain and dry cough. Initial symptoms led clinicians to believe the patient had hantavirus or bacterial pneumonia, resulting in treatment with piperacillin-tazobactam, vancomycin and azithromycin.

Despite receiving progressively intensive oxygen therapy, the patient’s hypoxemia worsened and he died less than 8 hours after being admitted to the ED — Arizona’s first pneumonic plague death since 2007.

According to the report, testing identified Y. pestis in blood cultures and blood and lung tissue.

Health officials investigated the patient’s actions in the days prior to developing symptoms to determine a possible source and identify any contacts. Investigators learned that 4 and 5 days before his symptoms developed, he had occupational exposure to two indoor domestic cats with symptoms consistent with pneumonic plague. Both cats were euthanized and unable to be tested for confirmation but “inhalation transmission” from either cat was possible based on the exposure, according to the report.

Although no other people reported symptoms, 46 potentially exposed contacts of the man, including household members, coworkers and hospital staff members, began a 7-day course of oral ciprofloxacin postexposure prophylaxis.

“Rapid collaboration by local, state, and federal public health officials was critical to identify the likely source of Y. pestis infection, identify contacts, offer post-exposure prophylaxis to reduce risk of secondary transmission, and identify gaps in diagnosis and treatment,” Marx said.

“Pneumonic plague is rapidly progressive and universally fatal without early effective treatment,” Marx said, noting that naturally occurring plague is treatable with commonly available antibiotics.

“Healthcare providers should consider early and empirical treatment for plague for patients in an endemic area who present with symptoms of plague and who report recent exposure to sick animals,” she said.

A similar case was reported in Oregon in 2024 when a man also contracted plague from his pet cat after cutting his finger on a kitchen knife and having close contact with the cat, which was being treated with oral antibiotics for a neck abscess and vomiting.

According to that report, the man noticed a new ulcer on his wrist and other symptoms, sought care and ultimately tested positive for Y. pestis via blood culture. The man made a full recovery by mid-February. The cat, however, died.

Grace Marx, MD, can be reached at media@cdc.gov.