A 28-year-old laboratory worker in Russia’s Siberian region of Irkutsk has died after developing pneumonia of unknown origin, according to CNN. The death has prompted quarantine measures and medical monitoring amid unconfirmed concerns about possible plague.

The woman worked at the Irkutsk Research Anti-Plague Institute in Shelekhov, a town near Lake Baikal. Local media identified her as Darya Shipilova.

Russia’s health watchdog, Rospotrebnadzor, said the woman had been diagnosed with pneumonia of unknown origin. It said no microorganisms linked to her professional duties were detected in samples taken from her.

The agency also said the epidemiological situation in the region was stable, CNN reported.

Nearly 200 People Reportedly Under Observation

Regional authorities have introduced anti-epidemic measures following the death. The hospital where the woman was treated has been placed under quarantine, with some departments stopping admissions and discharges.

CNN reported that unofficial information indicated nearly 200 people were under observation. Authorities said recent contacts of the worker were being tested and medically examined.

Rospotrebnadzor chief Anna Popova travelled to Irkutsk for an emergency meeting with regional officials.

The Kremlin has urged people to rely on official statements rather than unverified reports.

Plague Has Not Been Confirmed

The case has attracted attention because the woman worked at an institute that studies plague and other infectious diseases.

The governor of neighboring Buryatia said the woman had possibly died from plague. However, Russian health authorities have not confirmed plague as the cause of death.

CNN also reported that the institute did not comment on the incident when contacted.

Reports of a possible laboratory exposure have circulated, but the circumstances have not been independently confirmed. Rospotrebnadzor said no microorganisms connected to the employee’s work were detected in her samples.

Pneumonic plague is caused by the bacterium Yersinia pestis. It can be transmitted through respiratory droplets in certain circumstances. Early treatment with antibiotics can be effective.

WHO Says Public Health Risk Appears Low

The World Health Organization told CNN that it was communicating with Russian authorities to verify the case, its circumstances and laboratory test results.

Based on unofficial information available at the time, WHO assessed the risk to the general population as low.

US officials are also monitoring the situation. Secretary of State Marco Rubio said the administration was watching developments closely.

A US State Department spokesperson told CNN that many details remained unconfirmed and called for accurate and timely information from Russian authorities.

The investigation into the woman’s death is continuing. No outbreak of plague has been officially confirmed in Russia.