A woman's death in Siberia has prompted concern about pneumonic plague, but there is no confirmed diagnosis and experts say a global outbreak is unlikely. Laboratory tests are still being conducted to establish the official cause of death.
The woman, Daraya Shipilova, was 28 and worked at an anti-plague institute in Russia's Irkutsk region. She died of pneumonia last Friday. Unconfirmed reports linked her illness either to a broken test tube containing plague bacteria or to travel in Buryatia, a region bordering Mongolia where plague is locally found in wild animals.
Russian media reported that about 200 people had been placed in isolation. Officials have rejected concerns connected with plague, although online speculation and rumours have continued. The World Health Organization said all contacts of the patients had been identified and were being monitored, with no symptoms reported among them at the time described.
How pneumonic plague spreads
Plague is caused by the bacterium Yersinia pestis. It has three medical forms: bubonic plague, pneumonic plague and septicemic plague.
Bubonic plague is the most common form. It is usually transmitted through the bite of an infected flea. After entering the body, the bacterium reaches the lymph nodes and can cause painful swellings called buboes in the groin, neck and armpits.
Bubonic plague rarely spreads directly from one person to another. However, the bacterium can enter the bloodstream, causing septicemic plague, or reach the lungs and cause pneumonic plague.
Pneumonic plague differs because it can pass between people through small droplets released when an infected person coughs or sneezes. It is generally life-threatening, particularly when treatment is delayed. Symptoms can begin as soon as 24 hours after exposure.
That rapid progression also creates an opportunity for public-health teams to act quickly. Symptoms are usually serious and noticeable, allowing a new case to be identified, isolated and treated before further transmission occurs, according to the explanation provided in the report.
Why the present risk is considered low
The report contrasts modern conditions with the plague and pneumonia pandemic known as the Black Death. In the 14th century, it killed more than 2.5 crore people in Europe and wiped out between one-third and two-thirds of the population. The spread was associated with newly opened trade routes and the movement of goods, including grain and flour, on ships.
Modern treatment is a major difference. Untreated pneumonia caused by Yersinia pestis can be fatal, but the infection can be treated with widely available antibiotics.
Piero Olliaro, a professor of poverty-related infectious diseases at the University of Oxford, said there are two treatments for bubonic plague that work very well. In 2025, Olliaro and colleagues published the first trial of bubonic-plague treatment in Madagascar.
The trial found that oral ciprofloxacin and an aminoglycoside given by injection were 91% and 92% effective respectively for bubonic plague. Some patients developed pneumonic plague, but immediate treatment resulted in 85% recovering and surviving in those cases.
Another difference from COVID-19 is that pneumonic plague spreads only after symptoms begin, according to the report. The illness generally develops within 24 hours, leaving a short but important window for identifying and isolating patients and providing treatment.
Monitoring and laboratory safeguards
The World Health Organization's initial risk assessment placed the risk at medium to low for Irkutsk, low for the Russian Federation and very low for the WHO European Region. WHO spokesperson Christian Lindmeier announced the assessment on Tuesday and said contacts were being followed.
The approach is consistent with advice from the US Centers for Disease Control and Prevention. That guidance recommends identifying people who may be at risk so they can be monitored and tested, with antibiotics provided after assessment where appropriate.
The report also notes that laboratory-acquired infections are extremely rare because laboratories generally use strict protocols to prevent accidental exposure. Zania Stamataki, an associate professor of viral immunology at the University of Birmingham, said specialised laboratories have several layers of safety.
Those safeguards include full personal protective equipment for researchers and handling samples only inside biological safety cabinets. These measures reduce the possibility of accidental infection, although Stamataki cautioned that plague should not be ignored.
Conclusion
The reported death remains under investigation, and the official cause has not been established. The available assessment is that widespread transmission is unlikely because of effective antibiotics, rapid symptom onset, contact monitoring and layered laboratory protections.
Frequently Asked Questions
Q. Has pneumonic plague been confirmed as the cause of the woman's death?
No. Laboratory testing is continuing, and the official cause of death remains unknown.
Q. Where did the reported case occur?
The woman worked at an anti-plague institute in Russia's Irkutsk region, in Siberia.
Q. How many people were reportedly placed in isolation?
Russian media reported that about 200 people were placed in isolation.
Q. How does pneumonic plague spread?
It can spread between people through small droplets released when an infected person coughs or sneezes.
Q. Can plague be treated?
Yes. The report states that Yersinia pestis infections can be treated with widely available antibiotics.
Q. What risk did the WHO assessment identify?
The assessment described the risk as medium to low for Irkutsk, low for the Russian Federation and very low for the WHO European Region.
Q. Are contacts showing symptoms?
The WHO said identified contacts were being monitored and that none had symptoms at the time described.
Q. Why are laboratory infections considered rare?
Strict safety protocols, personal protective equipment and biological safety cabinets are used to reduce accidental exposure.
