Nearly 200 people have been placed under precautionary medical observation in Russia’s eastern Siberian region of Irkutsk following the death of a laboratory worker at an anti-plague research institute.
She was suspected of having been exposed to pneumonic plague.
According to NBC, 189 individuals who had come into contact with the researcher are currently being monitored.
The female employee, reported by different local outlets to be 27 or 28 years old, fell ill after returning from a work trip to the neighbouring Republic of Buryatia near the border with Mongolia, where a plague outbreak had been reported.
Alexei Tsydenov, head of the Republic of Buryatia, stated that the woman had died from an unspecified form of plague.
However, Russia’s public health watchdog, Rospotrebnadzor, stated on Sunday that the employee had been diagnosed with “pneumonia of unknown etiology.”
Moreover, they maintained that the overall sanitary and epidemiological situation across the Irkutsk region and the cities of Irkutsk and Shelekhov remained stable.
The consumer welfare service added that expanded testing failed to detect microorganisms linked to the worker’s laboratory duties.
Meanwhile, Maksim Modin, mayor of the Shelekhov municipal district, confirmed that the inpatient medical facility where the researcher received treatment had been closed for quarantine.
The incident has prompted international concern and calls for greater official transparency.
The US State Department confirmed it is closely monitoring the situation alongside the Centers for Disease Control and Prevention (CDC) and other agencies.
“Many details have not been confirmed. We encourage Russian authorities to share accurate information quickly and openly,” the department said in a statement.
Axios reported that White House and Trump administration officials are assessing options.
Moreover, Dr Ashish Jha, who served as White House Covid-19 response coordinator from 2022 to 2023, demanded “much more” transparency from Moscow, noting that if biological weapons programmes existed in such laboratories, it would be “much more concerning”.
Jha added that if this remains an isolated case with no further deaths, “it will probably end there”.
Pneumonic plague, caused by the same bacterium as bubonic plague, can spread from person to person through airborne respiratory droplets from coughing or sneezing and requires rapid treatment with powerful antibiotics.
While the World Health Organisation (WHO) warns that the disease is highly contagious and can trigger severe epidemics, Jha stressed that human-to-human transmission is difficult, making the likelihood of a major outbreak or global pandemic exceedingly low.
According to WHO data, ten countries reported over 3,800 suspected human plague cases between 2019 and 2025, resulting in 423 deaths, primarily in Madagascar and the Democratic Republic of the Congo.
