Last week, a 28-year-old lab technician in Russia died of suspected pneumonic plague, leading the United States and World Health Organization (WHO) to monitor the situation for a potential outbreak.

Woman dies of suspected plague in Russia

Last week, a 28-year-old woman named Darya Shipilova who worked as a lab technician at the Irkutsk Anti-Plague Research Institute of Siberia and the Far East was sent to the hospitals with symptoms of severe pneumonia. She later died overnight between Oct. 1 and Oct. 2.

Although there has not been a confirmed cause of Shipilova's death, Russian media reported that she had broken a test tube containing a pneumonic plague pathogen. Igor Kobzev, governor of Irkutsk, also held an emergency meeting with regional anti-epidemic officials and the head of Russia's national public health agency Rospotrebnadzor, in response to a "suspected case of a particularly dangerous infection" affecting someone in the region.

Separately, Alexey Tsydenov, head of the neighboring region of Buryatia, said that Shipilova "possibly died of the plague," while noting that there were no reported outbreaks of the disease in his region.

Plague is an infection caused by the Yersina pestis bacteria and has three main forms: bubonic, pneumonic, and septicemic. Pneumonic plague is the rarest form of the disease, but it is also the most virulent and the most dangerous. While human-to-human transmission of bubonic plague is rare, pneumonic plague can be spread through respiratory particles.

Symptoms of pneumonic plague include fever, headache, weakness, quickly developing pneumonia, chest pain, shortness of breath, and more. Symptoms can appear quickly after infection, sometimes within 24 hours, and if the infection is not diagnosed and treated early, it is fatal.

"It's the one that's so frightening because it can kill so quickly," said Lisa Morici, a microbiologist and immunologist in the Tulane University School of Medicine.

According to Morici, people with pneumonic plague are often quarantined, and healthcare workers will wear personal protective equipment, such as an N95 mask or even a full body suit, in case of accidental exposure.

So far, local authorities have placed almost 200 people who may have had contact with Shipilova under medical observation. Five hospitals, including one for children and one for maternity, continue to be under quarantine due to the incident.

US, WHO to monitor the situation in Russia

On Sunday, Axios reported that the White House was monitoring the situation in Russia. The State Department later told ABC News it was "aware of reports of a fatal case of suspected pneumonic plague in Irkutsk Oblast, Russia," and that it was "monitoring the situation closely with the CDC and our other interagency partners."

Lindmeier noted that based on "unofficial information … the public health risk to the general population appears to be low."

WHO has also requested information about media reports about "a second employee with pneumonia of undetermined cause." So far, the reports have not been verified, and it's not clear if another individual has been infected or died from the plague.

In response to the reports of a second potential plague death, Dmitry Peskov, a Kremlin spokesperson, urged caution when using media reports as a reference for what was occurring. "There is a great deal of media coverage, and the vast majority of what the media are reporting about this situation is false information," he said.

In a statement released late Sunday, Rospotrebnadzor said the "sanitary and epidemiological situation" in Irkutsk and Shelekhov was "stable." The public health agency also said it conducted extensive testing and found no pathogens linked to Shipilova's laboratory work. So far, no infectious diseases or illnesses have been reported among those under quarantine either.

Should you be worried about the plague?

According to WHO, "pneumonic plague is especially contagious and can trigger severe epidemics through person-to-person transmission via respiratory particles."

However, close contact is typically required for the infection to spread since the respiratory particles only travel short distances, roughly three to six feet.

Pneumonic plague isn't something that spreads "distantly across a room, but to face-to-face contacts," said William Schaffner, an infectious disease expert.

"It's highly unlikely for most people to get the pneumonic form of the disease," Morici said, adding that "[i]t's nothing like the COVID-19 pandemic."

Although plague is no longer common, CDC data shows that the United States sees about seven cases each year. Most plague cases occur in rural parts of the Southwest where the Yersina pestis bacteria naturally circulate in wild rodents and their fleas. Around 80% of plague cases in the United States are the bubonic form of the disease, which is not usually transmitted between humans.

Notably, plague, in all its forms, is also easily treatable with antibiotics if it is diagnosed early enough. For pneumonic plague, if symptoms are treated within 24 hours of symptom onset, recovery rates are high.

"We will not turn 2026 into the Middle Ages, where the Black Death caused vast amounts of death throughout Europe," Schaffner said. "That will not happen." He also noted that there is no evidence to suggest that plague bacteria are evolving to become resistant to antibiotics.