Various media outlets are reporting the death of a woman named Daria Sifilova, who worked at a laboratory where she accidentally contracted the plague; she fell ill and died between October 1 and 2. The head of the neighboring Buryatia region initially wrote that she had died of the plague but later edited the message to say "possibly"—effectively turning a definitive statement into a mere "maybe."
At this moment, there is no official confirmation that the plague was the cause of death. You might be wondering why a laboratory would research such a dangerous bacterium—one that once devastated entire cities. Well, the laboratory in question was established in 1934, during the Soviet era, and its function is like that of any other lab researching pathogens (and there are others like it around the world): to seek out cures and vaccines—in this case, a cure for the plague.
Research also covers other pathogens like anthrax, but the plague is part of the investigative scope; in fact, natural reservoirs of pneumonic plague—the most primitive version—exist in Siberia. Moreover, the origin of the plague outbreaks that devastated humanity is believed to lie precisely there, stemming from an initial transmission—possibly via a marmot eaten by a group of hunter-gatherers living near Lake Baikal about 5,500 years ago, very close to the modern-day city of Irkutsk. This ancient transmission event is detailed in a study published on June 17, 2026, in the scientific journal *Nature*.
Returning to the case at hand—which, I repeat, is not officially confirmed (a sensitive matter that must be clearly stated to avoid complications)—even if it were the plague, it would not be the type associated with the great historical epidemics transmitted by rat fleas. Even a bacterium of that kind would have very limited potential today, as modern cities possess far more effective sewage and waste management systems than those of the Middle Ages or the Roman Empire.
Rat populations are now much more strictly controlled and limited; there is no longer the direct contact between rodents and human-inhabited areas that existed in the past. The suspected diagnosis in this case is pneumonic plague—the pulmonary form found in certain wild Siberian mammals, such as marmots. While it is a very serious illness, transmission is difficult; it spreads via droplets, requiring close proximity to the patient.
It is nowhere near as contagious as a virus like COVID or the flu; those viruses can travel several meters through the air—partly because they are viruses rather than bacteria. Viruses are much smaller and have a far more basic structure than bacteria. In fact, most experts do not consider viruses to be living organisms because they lack cells and their own metabolism, whereas a bacterium is a single-celled organism with its own metabolism and is far more complex than a virus. To use an analogy: if a bacterium were a human, a virus would be like a zombie—not a whole human zombie, but just a zombie hand. Because they are so basic and lightweight, viruses can travel inside aerosols—liquid particles far smaller than standard droplets. These aerosols can remain suspended in the air of a closed room for minutes or even hours, drifting like cigarette smoke; as you can imagine, this exponentially increases their potential for transmission, which is why ventilating rooms is so often recommended.
Let’s assume this was the cause—though I repeat, this is speculation and has not been confirmed. According to the World Health Organization, the incubation period can be incredibly short—just 24 hours—and without treatment, it kills within 18 to 24 hours of symptom onset; there are no survivors. In fact, a review of cases published by the CDC (the U.S. Centers for Disease Control and Prevention) places the fatality rate for untreated pneumonic plague of this type at around 98%. If you are wondering about the great plagues of antiquity, they were not of this type; they were the bubonic plague variant transmitted by rodent fleas. Without antibiotics, the WHO estimates a fatality rate of 30% to 60%. During outbreaks like the Black Death, the pneumonic form also circulated—the only type that spreads from person to person through the air—which is why some cities lost half their population in a matter of weeks or months.
The plague was more devastating and efficient than war; in just a couple of weeks, it could wipe out half a city's population. However, we are no longer in the Roman Empire or the Middle Ages—we are in the 21st century. If symptoms are detected and treated within the first 24 hours, experts estimate an 83% survival rate for pneumonic plague—the deadliest form if left untreated. In other words, according to a CDC review, 83% of people treated for pneumonic plague can survive.
It is not a guarantee, and it depends largely on how quickly the disease is detected and whether antibiotics are administered in time. However, it is important to note that the scenario described above assumes the cause was the plague bacterium. In conclusion, while the researcher's death is confirmed, it has not been officially confirmed that the plague bacterium was the cause; as of this report, Russian authorities have not stated the cause of death.
Media outlets also report that nearly 200 of the deceased's contacts—people from her circle—are currently under medical observation. This does not mean there is an outbreak; it is a control measure, and no outbreak has been confirmed. Meanwhile, the United States is closely monitoring the situation; specifically, Senator Marco Rubio stated that the death of this Russian plague researcher is—to quote him—a matter for attention, but not for alarm.
We will continue to follow this story. What do you think?
