The World Health Organisation has demanded more information following the death of a laboratory worker at a Russian plague research laboratory.
Danya Shipilova, 28, a laboratory worker at the Irkutsk Research Anti-Plague Institute in Shelekhov, Siberia, died on October 2 after developing pneumonia of undetermined cause.
Russia has placed more than 200 people in quarantine after the incident.
The circumstances surrounding her illness, and the nature of the research conducted at the institute, have raised international concern about the potential threat of a plague outbreak. However, Russian authorities have denied reports of a confirmed case of pneumonic plague in the region.
The World Health Organisation has asked Moscow to provide more details about the incident, including laboratory test results for Ms Shipilova and those placed in quarantine.
At a media briefing on Wednesday, WHO director general Tedros Adhanom Ghebreyesus said Russian authorities had held a meeting on October 2 after a resident of Irkutsk Oblast in Eastern Siberia was suspected of having contracted a dangerous infection.
“WHO has asked the Russian Federation for more information in accordance with the International Health Regulations,” Dr Tedros said.
“The Russian Federation responded, saying that no case of plague had recently been reported in the Irkutsk Oblast and that they had placed about 200 contacts in quarantine.”
The WHO has requested additional information about laboratory testing, the reasons for the public health measures and the health status of those who were quarantined. It has also asked Russia to clarify media reports about a second employee who allegedly developed pneumonia of undetermined cause.
Dr Tedros said the WHO had offered technical support on plague and laboratory biosafety and biosecurity but had not been able to conduct a full risk assessment or establish a complete picture of what had happened.
“Timely, complete and transparent information sharing under the International Health Regulations is essential to clarify conflicting reports and enable an accurate assessment of potential public health risks,” he said.
The US and the EU have also urged Russia to be transparent about the incident.
Kremlin spokesman Dmitry Peskov had rejected media reports about the suspected plague case.
Risk to public
The US Centres for Disease Control and Prevention said it was monitoring developments.
“We are working across the US government to assess developments as additional information becomes available,” the CDC said.
“While the circumstances of this reported case remain unconfirmed, plague is a serious bacterial disease that is treatable with antibiotics, particularly when recognised and treated early.
“At this time, there is no indication of a broader threat to the US,” the CDC said.
The CDC added that pneumonic plague can spread through respiratory droplets during close contact. Rapid identification and treatment of infected people, together with monitoring of potentially exposed individuals, are important public-health measures.
What is pneumonic plague?
Pneumonic plague is a severe lung infection caused by the bacterium Yersinia pestis. It is the most serious form of plague.
How does it spread?
Close contact: Pneumonic plague can spread when an infected person coughs or sneezes and someone else inhales the respiratory droplets.
Infected animals: Rarely, people can be exposed to respiratory droplets from animals with pneumonic plague, including domestic cats.
Secondary infection: Bubonic or septicaemic plague can progress to pneumonic plague if the bacteria reach the lungs.
What are the symptoms?
Symptoms usually appear quickly, within three days of exposure, but sometimes as long as a week after contact.
They include sudden fever, chills, headaches, weakness and shortness of breath, similar to some seasonal illnesses such as influenza.
These symptoms can be followed by rapidly worsening pneumonia and chest pain with coughing that frequently produces bloody or watery mucus.
Is there a treatment?
Yes. Plague can be treated with antibiotics, particularly when treatment begins promptly. Because pneumonic plague can progress quickly and can be fatal without treatment, suspected cases require urgent medical assessment, isolation and appropriate antibiotic dosage.
Antibiotics used to treat plague can include gentamicin, doxycycline, ciprofloxacin and moxifloxacin, depending on the clinical circumstances and medical guidance.
Recent plague cases
Arizona, US, July 2025: A man died from pneumonic plague a week after exposure to sick cats. Despite receiving antibiotics and oxygen, the man died within eight hours of his admission to hospital.
Global endemic areas: The bacterium Yersinia pestis is active in wild rodent populations in about 26 countries. Seasonal cases are reported most frequently in Madagascar, the Democratic Republic of the Congo, and Peru. There are about seven cases a year in the US, mainly in the western part of the country.
