Russian health authorities have reportedly placed hundreds of people in quarantine in Siberia following the death of a laboratory worker who was exposed to an “unknown” virus.

The 28-year-old victim was an employee at the Anti-Plague Research Institute in Shelekhov, a town near the regional capital of Irkutsk, according to reports.

Prior to her death, she reportedly told medical personnel that she had accidentally broken a test tube containing live biological samples while working inside the facility.

She was subsequently hospitalised with severe pneumonia of “unknown origin,” placed on a ventilator, and died shortly after on Thursday.

State consumer safety watchdog Rospotrebnadzor said that emergency sanitary protocols were immediately enacted following a case involving “pneumonia of unknown etiology” at the facility.

Since, Rospotrebnadzor has maintained that the broader situation in the Irkutsk region remains stable.

At least 197 people suspected of having direct or indirect contact with the technician have been placed under medical isolation, according to independent regional news outlet Liudi Baikala. More than 100 of those individuals are currently being monitored in hospital wards.

At the same time, local authorities have instituted strict quarantine measures across the district, targeting the Shelekhov District Hospital, a nearby maternity facility, and a local aluminium plant.

Irkutsk Governor Igor Kobzev urged residents to remain calm, writing on Telegram that an anti-epidemic commission convened to address a “suspected case of a particularly dangerous infection.”

While his public statement did not acknowledge the worker’s death, Kobzev stated that all identified close contacts remain asymptomatic and have tested negative.

Russian law enforcement agencies have reportedly opened a criminal investigation into potential workplace health and safety violations resulting in the lab worker’s death.

Former Rospotrebnadzor head Gennady Onishchenko downplayed the threat in comments to state news agency TASS, stating that the infection in the Irkutsk region is “most likely not the plague, but even if confirmed, there will be no spread of this disease.”

He added that widespread transmission remains unlikely, noting that cooler seasonal temperatures would help contain potential spread.

Because the facility specialises in dangerous pathogens, the incident has drawn speculation it could be pneumonic plague – one of three variants caused by the bacterium Yersinia pestis.

Unlike bubonic and septicemic plagues, which generally pass to humans via flea bites or contact with infected animals, pneumonic plague attacks the lungs directly and can easily spread from person to person through airborne respiratory droplets.

According to guidelines from the US Centres for Disease Control and Prevention, patients infected with pneumonic plague typically experience rapid onset fever, headaches, and physical weakness, alongside severe respiratory distress such as shortness of breath, chest pain, coughing, and watery or blood-tinged mucus.

While the World Health Organisation (WHO) warns that the disease carries a high mortality rate if untreated, it remains highly manageable with early antibiotic administration and standard infection control measures.