Since early October, American and other Western health and biodefense officials have been concerned by reports on social media that a young Russian researcher at an anti-plague institute in Siberia had died of a highly contagious form of plague after accidentally breaking a vial of the deadly germs in her laboratory.
While much remains unknown about the mysterious death of the female researcher in Irkutsk, this much now seems clear: Darya Shipilova, the researcher, was a 28-year-old junior scientist at the Anti-Plague Institute of Siberia and the Far East in Irkutsk. While the Russian health authorities belatedly asserted that she had died not of plague, but of pneumonia of unknown origin, they declined to identify the pathogen that caused her death or to describe the specific nature of her work at the institute. But Shipilova had recently coauthored a paper on a study of more than 230 strains of plague. The study, signed by her and six other scientists, concluded that the wild plague strains studied were highly susceptible to nine of the most widely used antibiotic drugs to counter the deadly germs.
The paper, presented in March at the 18th annual All-Russian Congress on Infectious Diseases in Moscow, indicates that Shipilova, who died on Oct. 2 of still uncertain causes, had at the very least done research on plague bacteria known as Yersinia pestis, which is endemic in Siberia among the region's wild rodents and fleas. The existence of the paper was initially reported by Healthbeat, a newsletter, which did not point out that the research on antibiotic susceptibility is the type of dual-use research that anti-plague institutes in the Soviet Union historically have conducted to identify antibiotic-resistant strains for the country's top-secret biological weapons program.
Following her unexplained death, social media and at least one regional official said that she had died from pneumonic plague, a highly contagious form of the pathogen that is spread from person to person, and that Russian authorities feared a broader outbreak of the deadly disease. These rumors quickly went viral on social media. Some 200 people at her lab, the hospital in Shelekhov where she died, and others in her neighborhood had been quarantined for several days, according to Meduza, an independent Russian news outlet, which quoted a report by a regional Russian media outlet, People of Baikal, which sent reporters to Irkutsk and the town of Shelekhov to investigate her death. Russian health authorities had taken other emergency measures to prevent the spread of the dangerous pathogen, they reported, such as twice disinfecting the building where Shipilova lived, and having the Federal Security Service—the FSB, the KGB's successor—take those who had been in contact with her to quarantine in ambulances. People of Baikal also reported that Shipilova had told medical staff she had accidentally broken a test tube containing the plague pathogen while handling samples on Sep. 25.
The news outlet reported that Shipilova was hospitalized on Sep. 29 and died three days later on Oct. 2. Gov. Igor Kobzev was quoted as saying that the reason was "a particularly dangerous infection." But neither he nor other official statements mentioned the word plague. Other officials also reported her death as the result of a dangerous germ, but those reports were subsequently deleted after Russian health officials made an emergency visit to the region.
After initially having said virtually nothing about the incident, Rospotrebnadzor, the Russian health regulator, issued a series of statements following requests from the United States and the World Health Organization for more information about her death. The regulator said that Shipilova had died of a "pneumonia of unknown origin" and that she had "immunity to the dangerous infections she worked with," suggesting that she had been vaccinated against plague bacteria. The tests on Shipilova's remains had found "no evidence" of any of the pathogens she had worked with at the institute, and two commissions that inspected the institute had found "no emergency situations ... with pathogenic microorganisms." Nor had any dangerous germs been detected in the nearly 5,000 lab tests conducted there. Medical "observation" of more than 90% of the people she had been in contact with had been completed, the regulator's statement said. "Preventive and anti-epidemic measures have been organized to an exhaustive extent," the statement said. "There are no epidemiological risks for the population of Irkutsk and the Irkutsk region."
These statements, however, have not quelled international concern about Shipilova's death given Russia's and the former Soviet Union's well-documented history of covering up its extensive, illegal biowarfare activities. After the Soviet Union signed the Biological and Toxin Weapons Convention in 1972 and ratified the treaty banning bioweapons in 1975, Moscow dramatically expanded its secret bioweapons program—which, at its peak, involved roughly 40,000 to 60,000 scientists across more than 40 institutes and production plants. The Soviets continued to lie about the existence and purpose of Biopreparat, the cover name for the secret biowarfare effort, until defectors in the late '80s and early '90s exposed the scale and the nature of the program to British and American officials.
The anti-plague research institute where Shipilova worked was one of six such Soviet institutes that were once part of that massive biowarfare effort. Their historic role included collecting, characterizing, and enhancing dangerous pathogens that would then be passed to the closed biological weapons facilities. In the late 1990s, we visited the Anti-Plague Institute in Almaty, Kazakhstan, where we saw a collection of more than 1,000 lethal germ strains that were protected by only a rickety wooden door and a single skeleton-key lock. During the visit, Weber was permitted to hold a rusty pea can that contained enough plague in a glass tube to sicken the entire region.
Estimates prepared by William Patrick, the late American expert on the American and Soviet bioweapons programs, put annual Soviet production of dried Yersinia pestis at 1,500 metric tons a year. Patrick asserted that the United States did not produce that pathogen for weaponization. Richard Nixon ended the American biological weapons program in 1969, which Patrick had been a part of for many years.
While Russia falsely claims that it is now conducting only biodefense research, foreign officials have not been permitted to visit many of these institutes and have never gained access to those run by the Russian military. This year, U.S. intelligence agencies asserted that Russia is continuing to develop new chemical and biological weapons capabilities. In its arms control compliance report in 2025, the State Department said that Russia has maintained an offensive bioweapons program in violation of the Biological Weapons Convention.
Russia's initial silence about Shipilova's death, its actions in Siberia after her death, and the conflicting statements issued by various Russian officials have all stoked concern among biodefense experts. While the World Health Organization and Washington have asked Russia for more specific information about the cause of her death, as well as for forensic evidence to support its explanation, Russia has yet to respond. But Russia's health authorities have denied that a second employee at the institute was suffering from a grave infection of undetermined origin, as an unverified report on social media asserted. And they maintain that Shipilova was vaccinated against the germs she worked with at the institute, yet decline to identify them. Russia has not released any primary documentation to support its claims—no autopsy, lab reports, or commission findings.
As a result, plague experts are anxious about the possibility that Shipilova died not of pneumonia, as Russia asserts, but of exposure to a highly virulent strain of plague that was multidrug-resistant and did not respond to the vaccine she had been given. David Relman of Stanford University, an expert on plague, said in an interview that this was one of several possible explanations for her death and Russia's lack of transparency. Stressing that one could only speculate given the lack of concrete evidence, he said an alternative explanation is that Shipilova had received what scientists call an "overwhelming dose" of the bacteria. "No vaccine is perfect," he said in an interview. Or, he added, echoing a speculation that troubles many biodefense experts, she might have been exposed to a strain that had been genetically modified to enhance its lethality, which, in turn, overcame her vaccine's protection. Any of these scenarios could have triggered her illness, he said.
A less-ominous explanation, and one Relman said he considered the most plausible, is that there had been an accidental exposure to a highly virulent strain in her lab that she didn't recognize at the time. "She would have just lived her life till the day she started getting sick," he said. After a few more days, it would have been too late to administer an antibiotic, which, to be effective against pneumonic plague, must be taken no later than a day or two after the onset of symptoms and ideally soon after exposure to a virulent pathogen. This scenario would also explain Russia's decision to quarantine hundreds of people in the area.
What didn't make sense, Relman said, was the initial report on social media that she had broken a vial of plague in the lab. "Who uses breakable glass vials these days?" he said. Plus, "she was an experienced, well-trained lab technician. If she had dropped something and knew she had been exposed to Yersinia pestis, why wouldn't she have immediately started prophylactic treatment—taking an antibiotic to protect herself?"
Perhaps she was one of those scientists who assumed that "bad stuff won't happen to them," he speculated. "Or maybe she did recognize the danger but decided not to worry about it. Perhaps she feared being punished, and preferred to hope for the best."
"There are so many things in what we've heard so far," he said, "that just don't hang together."