What to know about a Russian lab worker's death and speculation about pneumonic plague

Local officials have confirmed the illness and death of a lab worker at an anti-plague research institute in Russia.

A lack of transparency about the events and conflicting reports about the type of illness and how the young woman was infected have fueled concerns and speculations about a suspected case of pneumonic plague.

In a statement to state media, the country's health and consumer protection agency, Rospotrebnadzor, said the employee was diagnosed with "pneumonia of unknown etiology."

However, a local official previously described the woman as having died "possibly from plague."

Secretary of State Marco Rubio said the U.S. was aware of the incident and "monitoring it closely."

"I don't think it's cause for alarm, but it is cause for focus," Rubio told reporters Monday.

Here's what we know and don't know so far.

What are official sources saying?

Official accounts have varied.

The woman's name and age have not been confirmed. But officials say she worked at the Irkutsk Anti-Plague Institute of Siberia and Far East, which focuses on plague control and works with dangerous bacterial and viral infections, according to its website. The research body is located in the city of Irkutsk, about 3,000 miles east of Russia's capital, Moscow, and north of Mongolia.

Maxim Modin, the mayor of Shelekhovsky, a district of Irkutsk Oblast, confirmed a quarantine was in place at the Shelekhovsky District Hospital, in Telegram posts on Oct. 1 and 2, after saying he received many messages from residents asking for updates.

He said the hospital had suspended discharges and admissions and laboratory operations, but the outpatient clinic was still operating. He did not mention the lab worker's death or illness. A local outlet reported the lab worker had died at the Shelekhovsky hospital.

READ MORE: A Russian report says a worker at a Siberian plague research institute fell ill and died of an unknown cause

On Oct. 2, Igor Kobzev, governor of the Irkutsk Oblast region, confirmed via a Telegram post that he was hosting an "extraordinary meeting of the regional sanitary and anti-epidemic commission" with the head of Rospotrebnadzor. The country's chief sanitary doctor, Anna Yuryevna Popova, was in attendance.

Kobzev said the meeting occurred after information emerged "about a suspected case of a regional resident with a particularly dangerous infection."

He described the situation as "under strict control," and said the consumer protection agency had implemented "a full range of anti-epidemic measures."

That same day, Alexey Tsydenov, the head of the neighboring Republic of Buryatia, described the woman's death as being caused by the "plague," as he was responding to reports that she had previously traveled to the region. News outlets say Tsydenov later edited the post adding the word "possibly."

"There are no plague outbreaks in the republic, including in the area bordering Mongolia," he said. "The source of the infection is circumstances unrelated to Buryatia."

On Oct. 4, Rospotrebnadzor told state news agency TASS that it was responding to a case involving a lab employee "who was diagnosed with pneumonia of unknown etiology." The agency did not mention the woman's death.

On Monday, Kobzev echoed the consumer protection agency's wording, but described it as the woman's cause of death.

He clarified that "microorganisms associated with her professional activities were not detected in the patient's samples," and that no employees from the institute had sought medical attention in the past several days.

Local officials warned people not to visit the town of Shelekhov in a Telegram post that they later deleted, according to independent local news outlet People of Baikal.

What have local and independent media outlets said?

People of Baikal identified the worker as a 28-year-old lab technician and said she died of the pneumonic plague.

The news outlet cited local journalist Pavel Stepanov, who reported the lab worker was infected after she broke a test tube containing the pneumonic plague bacterium. It also reported that a state television channel deleted five articles it had published about the incident.

Rospotrebnadzor said in a statement to TASS that the institute had identified "no emergency situations involving pathogenic microorganisms."

Health authorities hospitalized 189 people who had been in contact with the lab worker, according to The Moscow Times, an independent Russian news outlet.

Local news outlet IrCity reported that a city cleanup event had been canceled as part of safety measures being taken "due to the unfavorable epidemiological situation."

What is the pneumonic plague?

Plague is a severe and often fatal disease caused by a bacteria known as Yersinia pestis, which is often found in small mammals and fleas, according to the World Health Organization. People are infected through bites from infected fleas, contact with infected tissues or inhalation of infected respiratory particles.

There are three main kinds of plague: bubonic, pneumonic and septicaemic. Bubonic plague is the likely cause of the Black Death, the pandemic that hit Europe in the mid-1300s.

READ MORE: The U.S. sees 7 plague cases a year. Here's why

Pneumonic plague is a respiratory disease characterized by rapidly developing pneumonia, shortness of breath, chest pain and cough, according to the Centers for Disease Control and Prevention. It generally develops as a secondary infection from untreated bubonic plague, which affects the lymph nodes.

Pneumonic plague is the most serious kind of plague, according to the CDC, and it can be transmitted from person to person. If diagnosed early, it can be treated with antibiotics.

What concerns does this incident raise of possible biological weapons?

Biosecurity experts have raised alarms following the news that the death could be linked to the pneumonic plague.

Investigative journalist Annie Jacobsen, author of "Biological War: A Scenario," said the anti-plague research institute where the woman worked had been used for biological weapons engineering during the Soviet era.

WATCH: Annie Jacobsen and Geoff Bennett discuss 'Biological War' on 'Settle In'

She added that the U.S. State Department believes Russia's illegal biological weapons program has continued.

Jacobsen said Russia is worried about eyes on the facility, describing the government as "working very hard to close down all information about this."

She voiced skepticism about the possibility that the woman became infected by breaking a test tube, and wondered whether the facility was milling the pathogen to create an aerosolized version. Pneumonic plague in the wild is transmitted by droplets, but a genetically modified variant that can spread through the air would be more contagious.

"All bets are off as to how transmissible it could potentially be," Jacobsen said.

Dr. Ashish Jha, a biosecurity expert and former White House COVID-19 coordinator, said he was "concerned" after gathering facts about the incident.

He cited unconfirmed reports that national security services had escorted ambulances.

"If accurate, that's not the posture of a routine natural outbreak, even a normal lab accident," Jha said in an X post on Sunday.

He said he has long been concerned about "an accidental release" from a country's biological weapons program, and urged Russian authorities to be more transparent about what happened.

"The number of labs working on dangerous pathogens is growing worldwide," Jha said. "That means incidents like this will happen more often in the months and years ahead."