Thousands of people have been quarantined in Russia after a 28-year-old lab worker died from suspected pneumonic plague, leading to concerns about global transmission.
Though it's rare, at least two deaths due to pneumonic plague have been reported in Arizona. The more recent
was a young adult male who died at Flagstaff Medical Center in July 2025, according to county, state and federal health officials.An Oct. 1report from the U.S. Centers for Disease Control and Prevention says the man had experienced symptoms for two days before he sought medical help at the Flagstaff Medical Center emergency department. The man died on the same day that he went to the hospital to get help.
The man's death was the first recorded pneumonic plague death in Arizona
since 2007, according to the CDC and the Coconino County Department of Health and Human Services.
The cause of the 2025 pneumonic plague case could not be 100% ascertained, but the man who died had been exposed to ill indoor domestic cats through his job prior to getting sick. The cats, who were euthanized before the man became sick, had respiratory symptoms and other signs of illness "consistent with pneumonic plague" during the one to five-day incubation window before the man showed symptoms, the report says.
"Inhalation transmission from either cat was possible with the patient’s occupational exposure," according to the report.
The man sought help after two days of abdominal pain, chest pain, and dry cough, the CDC report says. The patient was admitted and received antibiotic treatment with piperacillin-tazobactam, vancomycin, and azithromycin. Despite "progressively intensive oxygen therapy" his poor oxygen levels worsened, and he died less than eight hours after he arrived at the hospital, according to the report.
What is the pneumonic plague?
Plague is caused by the bacterium Yersinia pestis, which is transmitted by fleas, and cycles naturally among wild rodents. Humans usually get the plague after being bitten by an infected rodent flea or by handling an infected animal. People may also become infected through exposure to sick pets, especially cats, the CDC says.
A 2015 CDC report characterized pneumonic plague as the least common of the three main forms of plague. The other two main forms are bubonic and septicemic. Pneumonic plague is especially dangerous because it is transmitted through inhalation of respiratory droplets containing the bacterium and has a nearly 100% case-fatality rate when untreated, according to the CDC.
The plague that killed millions of people during the 1300s and was sometimes known as the Black Death was primarily a combination of pneumonic and bubonic plague, according to the World Health Organization.
Has the plague reached the US?
It's less common now than it was in the Middle Ages, but plague cases and deaths still happen. Since the mid–20th century, plague in the United States typically has happened in the rural West, the CDC says. Yersinia pestis is endemic among rodents in Northern Arizona but it is not causing large outbreaks. Just 10 human plague cases were reported in Arizona between 2000 and 2026, federal and state records show.
The most recent case was confirmed April 7in a resident of Apache County, who fully recovered from the illness, county and tribal health officials said.
Federal surveillance data shows that between 1970 and 2023, Arizona recorded the third-highest number of plague cases in the country: 64. New Mexico, with 254 cases during that same time period, had by far the highest number. Colorado was second with 69 cases.
Dr. Jeanne Marrazzo, CEO of the Infectious Diseases Society of America, said that Americans should "remain calm" about the situation in Russia, but still "be vigilant."
Because of the location and many details left unconfirmed, the situation is raising questions.
"We don't really have a window onto what was going on at this research institute. Why were they studying plague?" Marrazzo said, adding this is a "dangerous pathogen."
"You would have expected if this happened that the worker would have immediately got prophylactic antibiotics." she said. "... We have no information about so many important things about this, I think it's something we just have to keep paying attention to and to be aware of."
Similarly, Jennifer Nuzzo, director of The Pandemic Center at Brown University, wrote in an Oct. 5 special report that though we don’t know enough about the case to conclude it presents a broader threat, several reported details are enough to raise concerns.
The first concern is that Russian authorities have reported that the laboratory worker died of an unknown cause, Nuzzo wrote. Though there have been reports that the patient tested negative for an unspecified list of pathogens, presumably to rule out plague, Nuzzo wrote that there is no available list of which pathogens were tested.
The most important question is: what did the patient have?, she wrote.
Second, reports detailing the local response indicate a high degree of health concern about the death. News articles indicate dozens of people are being monitored in Russia, and multiple hospital units are closed to admissions.
Third, the fact that the illness killed someone who worked with a plague, which is a naturally occurring pathogen that also tops lists of potential bioweapons, raises international concerns, Nuzzo wrote.
"Laboratory accidents can happen anywhere; strong biosafety and biosecurity protocols help ensure they don’t hurt anyone or extend beyond the lab," she wrote. "There may be commonplace explanations for what is happening. Coincidence and overreaction are possibilities. But we are, so far, unable to rule out more concerning explanations."
Sara Moniuszco of USA TODAY contributed to this article
Reach health-care reporter Stephanie Innes at stephanie.innes@usatodayco.com or follow her on X: @stephanieinnes or on Bluesky: @stephanieinnes.bsky.social.
This article originally appeared on Arizona Republic: What to know in Arizona about human pneumonic plague
