Russian authorities have imposed “anti-epidemic measures” after a laboratory worker at an institute in Siberia dedicated to studying the plague and other infectious diseases died of a mysterious illness.

The researcher, a 28-year-old female laboratory technician at the Irkutsk Research Anti-Plague Institute of Siberia, in the town of Shelekhov, died after being diagnosed with a pneumonia of “unknown” origin, according to Rospotrebnadzor, the Russian agency that handles infectious disease.

Authorities are implementing a “comprehensive set of anti-epidemic measures,” said Maxim Modin, the mayor of the Shelekhovsky district in eastern Russia, near the Mongolian border. The woman’s death was confirmed by officials last week.

The inpatient facility at the hospital where the worker was treated has been placed under quarantine, and several departments have stopped discharging or admitting patients, Modin said. Other hospitals in the region have also been closed, according to local media reports.

According to Rospotrebnadzor, “no microorganisms associated with the employee’s professional duties were detected in samples taken from the patient,” Modin said.

There have been no cases of infectious diseases reported among institute staff over the past 10 days, and all of the employee’s recent contacts are being tested and examined, Modin said.

Unofficial reports, including by the independent regional news outlet Liudi Baikala, have said that nearly 200 people are under observation.

Rospotrednadzor previously said the “sanitary and epidemiological situation” in Shelekhov and the state capital of Irkutsk was “stable.”

According to its website, the Anti-Plague Institute employs around 95 researchers and is a major research and public health facility responsible for monitoring and preventing outbreaks of high-risk bacterial and viral infections across Siberia and Russia’s Far East.

The head of the neighboring republic of Buryatia, Alexei Tsydenov, said earlier that the employee died “possibly from the plague.” He also noted that “there are no plague outbreaks” in Buryatia.

Pneumonic plague is one of three types of plagues that are caused by the bacterium Yersinia pestis and can transfer easily from person to person through respiratory particles.

The other two types typically spread from contact with infected fleas, animals or infected tissues.

An aluminum plant near the laboratory instructed staff to wear masks as a precautionary measure. The director of Irkutsk Aluminum Plant, Artem Fominikh, also urged calm and noted that “there are many rumors and conflicting reports circulating.”

The infection in the Irkutsk region is “most likely not the plague, but even if confirmed, there will be no spread of this disease,” a previous head of Rospotrebnadzor, Gennady Onishchenko, said on Friday.

Onishchenko told the state news agency TASS that the onset of cold weather would likely prevent transmission.

A US State Department spokesperson told CNN Sunday that it is aware of the possible death due to pneumonic plague in Russia.

“We are monitoring the situation closely with the CDC and our other interagency partners,” the spokesperson said. “Many details have not been confirmed. We encourage Russian authorities to share accurate information quickly and openly.”

Patients with pneumonic plague develop fever, headache, weakness and and “a rapidly developing pneumonia with shortness of breath, chest pain, cough, and sometimes bloody or watery mucous,” according to the US Centers for Disease Control and Prevention (CDC).

The US Department of Health and Human Services told CNN that the CDC is closely monitoring the situation in Russia, and that the “safety and security of U.S. citizens is our highest priority.”

The World Health Organization has noted that plague has a high fatality rate, but is also easily treated with antibiotics and the use of precautions to prevent infections. (CNN)

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