Could the Suspected Pneumonic Plague Case in Russia Lead to an Outbreak? Experts Weigh in

News of the mysterious death of a laboratory worker at an anti-plague research facility in Russia has swept the world, sparking concern about the risk of an outbreak, or even a pandemic. The medieval-sounding disease still causes a handful of cases around the world every year — yes, the plague never went away — and it’s fully treatable with antibiotics. However, the lack of information around the scientist’s death and the response from Russian authorities the has some experts on high alert. The 28-year-old woman, who worked as a lab technician at the Irkutsk Anti-Plague Institute of Siberia and the Far East, died last week of “pneumonia of undetermined” origin, NBC News reported, citing a Russian official, who did not link her death to her work at the lab. As of Wednesday, Oct. 7, her official cause of death has not been confirmed by Russian authorities. According to the Irkutsk regional governor, Igor Kobsev, no “microorganisms linked to the employee’s professional activities were detected” in her body, NBC News reported. However, a spokesperson for the U.S. State Department State Department said Monday that it was monitoring “reports of a fatal case of suspected pneumonic plague” in Irkutsk. The U.S. Centers for Disease Control and Prevention have also said they are “closely monitoring reports of a suspected case of pneumonic plague in the Irkutsk region of Russia that resulted in a death.” Pneumonic plague is a severe and often fatal lung infection caused by yersinia pestis, the same bacteria that causes the bubonic plague. It can spread from human to human by inhaling respiratory droplets. The staffer’s death has prompted at least one hospital, where she was treated, to enter quarantine, and nearly 200 people with whom she had contact with are under medical observation, NBC News reported, citing a local official and Russian media. The World Health Organization said on Tuesday that no cases of plague have been reported in the Siberian city of Irkutsk, quoting a response from the Russian government. Russia’s consumer and health watchdog, Rospotrebnadzor, also said in a statement that “no other infectious disease pathogens were detected among the contacts,” NBC News reported. Testing of the woman’s contacts identified two cases of COVID-19 and two cases of rhinovirus, which causes the common cold, per Rospotrebnadzor. According to Russian authorities, the “sanitary-epidemiological situation” in the Irkutsk region is “stable,” NBC News reported. There are still many questions about the scientist’s death, experts tell TODAY.com. The State Department is encouraging Russian officials to “share accurate information quickly and openly,” a spokesperson said. As the situation unfolds, rumors are circulating rapidly on social media, with many fearing another COVID-level pandemic. Here’s what experts think, and why plague may be not be as concerning. Pneumonic Plague Unlikely to Cause a Pandemic “The plague cannot cause widespread outbreaks the way it once did because we have antibiotics,” Dr. Amesh Adalja, a senior scholar at the Center for Health Security at the Johns Hopkins Bloomberg School of Public Health, tells TODAY.com. The suspected pneumonic plague case in Russia poses a “very low risk” outside of the country, the WHO said. “At this time, there is no indication of a broader threat to the United States, but CDC and our interagency partners are prepared and will continue to monitor the situation closely,” the CDC said in a statement posted to X on Tuesday. “Yes, the plague killed one-third of Europe’s population during the Middle Ages, but they didn’t even know what caused it,” says Adalja. Bubonic vs. Pneumonic Plague All three types of plague are caused by the same bacteria, yersinia pestis, but affect different parts of the body. Bubonic plague, the most common type, occurs when yersinia pestis infects the lymph nodes, says Adalja. It spreads to people through the bite of a flea carrying the bacteria or contact with infected animals, per the CDC. Septicemic plague is caused by the bacteria entering the bloodstream directly. Pneumonic plague, the rarest type, occurs when yersinia pestis infects the lungs. It’s spread by inhaling respiratory droplets from an infected person, but it can also develop if untreated bubonic or septicemic plague spreads to the lungs, Adalja notes. It’s the most virulent type of plague, per the WHO. “But it’s easily containable,” Adalja says. How Pneumonic Plague Spreads and Treatment Although pneumonic plague can transmit through airborne secretions, it doesn’t spread easily in this way. “It’s not a very efficient mode of transmission. Plague isn’t something that spreads in the manner of a virus. It’s nowhere near as contagious as COVID or influenza,” says Adalja. “It’s difficult to get unless you are in prolonged, direct, close contact with a sufferer,” Dr. Susan Jones, a veterinarian and professor at the University of Minnesota who has investigated plague in Russia, tells TODAY.com. Antibiotics are also highly effective at treating and preventing plague after a person is exposed. “Let’s say it is pneumonic plague. This woman worked at an anti-plague institute. They have post-exposure prophylaxis protocols, antibiotics,” Adalja explains. Ongoing Quarantines in Russia According to Russian media reports, quarantines are in effect at the Siberian hospital where the lab worker died, and 60% of her contacts have been tested so far, NBC News reported. It’s unlikely that potentially exposed contacts would’ve left Irkutsk on flights before being quarantined, Jones adds. Additionally, travel to and from Russia to the U.S. is very limited. Dr. Ashish Jha, the White House’s former COVID response coordinator, told NBC News that if this is an isolated case of pneumonic plague, “it will probably end there.” “Thousands of cases of pneumonic plague occur all over the world every year,” Adalja adds. Rarely do these cause outbreaks. “This is not the Black Death, and this is not COVID,” says Jones. Public Health Experts Are Still Concerned Not all experts are convinced pneumonic plague is to blame for the lab worker’s death. “I don’t even know where ‘plague’ came from, other than that it’s on the door of the building where she worked,” says Adalja. Lisa Morici, Ph.D., an immunologist at the Tulane University School of Medicine, told NBC News that “maybe it’s going to come out that she died from something unrelated and it was just a coincidence” that she was a technician at an anti-plague lab. It’s unclear if the deceased worker handled other pathogens. “It could be something else that’s more scary than plague,” says Adalja. The WHO has requested additional information to clarify the cause of the fatal pneumonia case and “media reports of a second employee with pneumonia of undetermined cause,” WHO Director-General Dr. Tedros Adhanom Ghebreyesus said in a post on X. The Russian government’s response to a potential isolated plague case also raises suspicion among some experts. “When you see contacts being monitored, hospitals being quarantined, the head of their public health agency flying there, that’s not congruent with the response for something as easy to handle as plague,” says Adalja. “What exactly was going on inside that lab that has led to the security services of Russia getting involved?” Jha told NBC News. However, Jones, who has visited anti-plague institutes in Russia, says the aggressive public health response is “normal” and follows protocol that dates back to Soviet times. “There (also) aren’t enough public health personnel to escort 200 people into quarantine, so security services are involved,” Jones explains. Symptoms of Pneumonic Plague After inhaling respiratory droplets from a person infected with pneumonic plague, it can take as little as 24 hours to develop symptoms, according to the CDC. The early signs of pneumonic plague include: FeverChillsWeaknessHeadache These can rapidly develop into pneumonia, leading to: Shortness of breathCoughingChest painBloody mucusRespiratory distress If left untreated, pneumonic plague is usually 100% fatal, per the WHO. The infection can be treated with antibiotics, but these are most effective when given early, within 24 hours of symptom onset, Jones adds. Pneumonic Plague in the US In the U.S., an average of seven cases of plague are reported every year, per the CDC. About 80% of these are bubonic plague. The disease has been in the U.S. since the early 1900s, when infected rats entered the country from ships, says Adalja. The last urban plague epidemic occurred from 1924-1925 in Los Angeles, per the CDC. Since then, the bacteria has spread to wild rodents, and most cases are scattered in rural areas. It’s now endemic to the Western U.S., and most cases are reported in Arizona or New Mexico, says Adalja. In 2025, a man in Arizona died of pneumonic plague after being exposed while working with infected cats, per the CDC. Overall, this type of plague is very rare — and unlike when the novel coronavirus emerged, scientists have the tools to fight it. “People are talking about plague as if it’s the 14th century and not the 21st century,” says Adalja. In the meantime, experts are calling for increased transparency and communication from Russia.