Μake us preferred on Google A death at a Russian research institute specializing in plague has renewed attention on pneumonic plague, a rare form of the bacterial disease that affects the lungs and can become fatal rapidly without treatment.
The 28-year-old researcher died after developing pneumonia of an “unknown” origin at the Irkutsk Research Anti-Plague Institute in Siberia. Several other people have been placed under quarantine, while Russian health authorities have played down a connection between the death and the researcher’s work.
The case is being monitored internationally. The US State Department and Centers for Disease Control and Prevention said they are following the situation, while the World Health Organization said it was communicating with Russian authorities to establish what happened, what tests are being carried out and whether there could be any international public health implications.
The WHO has said the available unofficial information indicates that the risk to the wider population is currently low.
What makes pneumonic plague different?
Plague is caused by the bacterium Yersinia pestis, but the infection can take several forms depending on where it develops in the body.
Bubonic plague, the most familiar form, generally follows an infected flea bite or entry of the bacterium through damaged skin. It is characterized by painful, swollen lymph nodes and can develop into septicemic plague, which affects the bloodstream and may cause organ failure.
Pharyngeal plague affects the throat and can occur after consuming infected meat.
Pneumonic plague, by contrast, involves the lungs and is regarded by scientists as the most dangerous form of the disease.
How can it spread?
As reported in CNN, pneumonic plague has a feature that distinguishes it from the other forms: it can be transmitted directly between people.
An infected person can release respiratory particles while coughing or sneezing. Infected animals can also transmit the disease through droplets.
Person-to-person transmission of pneumonic plague is rare in the United States. The country’s last documented such transmission occurred during a 1924 outbreak in Los Angeles.
What happens after infection?
The disease can progress quickly. Particles reaching the lungs can produce severe pneumonia and breathing difficulties, with symptoms potentially appearing within a day of infection.
Patients may also experience fever, chills, headaches, body aches, dizziness, weakness, fatigue, nausea, vomiting and diarrhea.
Without medical treatment, the disease is nearly always fatal.
Can pneumonic plague be treated?
Yes. Antibiotics can be used to treat plague, generally over a period of 10 to 14 days.
Treatment can involve drugs including ciprofloxacin, levofloxacin, moxifloxacin, gentamicin and streptomycin. The chances of survival are greatest when antibiotics are administered during the first 24 hours after infection.
Medical care may also include oxygen, fluids and other supportive measures.
Is there a plague vaccine?
Vaccines against plague have existed since the 19th century, but their ability to protect against pneumonic plague has remained uncertain.
The WHO does not recommend routine vaccination for the general population. Instead, it recommends vaccination for people facing particularly high exposure risks, including laboratory workers who are regularly exposed to the bacterium.
Why does plague still exist?
Plague is perhaps best known for its role in the Black Death, which killed more than 50 million people in Europe during the 14th century.
The disease has not disappeared, however. It remains present on every continent except Oceania, and the majority of human cases recorded since the 1990s have occurred in Africa, according to the WHO.
In the United States, the most recent death from pneumonic plague occurred in Arizona in July 2025. The victim, a young man who worked with sick cats, is believed to have contracted the infection from the animals. No other people exposed to the cats were reported to have become ill.
Infectious disease expert Dr. Tyler Evans has argued that ecological changes and reductions in public health infrastructure and measures could increase the risk posed by plague.
At the same time, he said the disease can be diagnosed relatively quickly and that the antibiotics used to treat it are highly effective.
How worried should the public be?
For now, health authorities do not consider pneumonic plague to pose a major risk to the general population.
The WHO has assessed the current risk as low based on the information available.
Dr. Rutul Dalal, an infectious disease physician at Penn State Health St. Joseph Medical Center, said the rapid development of symptoms can itself limit transmission because people infected with pneumonic plague can become severely ill within a short period.
Someone who is already experiencing significant symptoms may have difficulty carrying out everyday activities, including traveling.
Dalal also noted that there are no direct flights between Russia and the United States and said an infected traveler would likely be showing symptoms before reaching the US.
He stressed that the situation should continue to be watched but said it was not currently on the scale of the COVID-19 pandemic.
For people in close contact with someone who has plague, the WHO advises avoiding direct contact with sick individuals and taking precautions around infected bodily fluids. Healthcare workers treating pneumonic plague patients should use standard protective equipment and may receive preventive antibiotics.
Following an exposure, health officials can monitor family members and other close contacts and provide antibiotics before symptoms develop. Regular hand-washing with soap and water is also recommended.
