Researchers: International plague outbreak highly unlikely

In the Russian city of Irkutsk, a laboratory worker at a plague research institute has died of pneumonia of unknown origin; Russian authorities have stated that the death is unrelated to her professional duties, the BBC reports.

Darya Shipilova, 28, died on the 2nd of October following possible exposure to pathogens, and nearly 200 of her contacts were subsequently placed in quarantine. While officials have sought to allay concerns, various speculations regarding the incident are circulating online.

Shipilova worked at the Irkutsk Plague Research Institute. Unconfirmed reports suggest she fell ill and developed symptoms characteristic of pneumonia either after dropping a test tube containing the plague bacterium Yersinia pestis or following a research trip to the Buryatia region near the Mongolian border, where the plague is endemic among animals.

As of the 7th of October, the cause of Shipilova's death had not been officially confirmed, and laboratory investigations were ongoing. One thing is clear, however: experts believe that even if the death was caused by pneumonic plague, it is unlikely to lead to an international outbreak of the disease. Plague is caused by the bacterium Yersinia pestis. Clinically, it manifests in three forms: bubonic plague, pneumonic plague, and septicemic plague (which represents the fatal outcome of all clinical forms of the disease).

The bacteria enter the lymph nodes, and a painful bubo develops within six to eight hours. Human-to-human transmission of bubonic plague is rare, but the bacteria can enter the bloodstream, causing septicemic plague, or the lungs, causing pneumonic plague.

Unlike the other two forms, pneumonic plague can be transmitted to other people via respiratory droplets. If not detected early and treated with antibiotics, pneumonic plague is also fatal; furthermore, it has a much shorter incubation period—as little as 24 hours.

The so-called Black Death—caused by bubonic and pneumonic plague—killed more than 25 million people in 14th-century Europe, wiping out between one-third and two-thirds of the population. The spread of the plague was facilitated by new trade routes and the transport of grain and flour by ship, which also attracted rodents.

First, although Yersinia pestis is almost always fatal if left untreated, it can now be easily eliminated with simple, widely available antibiotics. Piero Olliaro, Professor of Poverty-Related Infectious Diseases at the University of Oxford, noted that there are two drugs that are highly effective against bubonic plague.

Another reason why a widespread pandemic is virtually impossible is that—unlike COVID-19—pneumonic plague is infectious only after symptoms have appeared; these symptoms usually manifest within 24 hours and are severe and obvious. This means that an outbreak can be quickly detected, and individuals can be isolated and treated before transmission occurs. Zania Stamataki, a professor of immunology at the University of Birmingham, stated that pneumonic plague is not something easily overlooked—the sort of illness where an infected person might board a plane and manage to spread the disease across half the globe.

According to information from the World Health Organization, all of Shipilova’s contacts have been identified and are being monitored, and none are showing symptoms of the disease. In a risk assessment published on the 6th of October, WHO representative Christian Lindmeier rated the risk of an outbreak in Irkutsk as moderate to low, in Russia as low, and for the WHO European region as very low.

Stamataki noted that these are highly specialized laboratories with a range of protective measures in effect. The professor explained that researchers wear full protective gear and handle samples inside special safety cabinets that maintain negative air pressure; this means air is drawn inward and away from the researcher, so that even if a sample breaks, the contents remain inside the cabinet rather than escaping into the air around the researcher.

Even when the test tube is being moved, it is placed inside another container to prevent the contents from escaping into the external environment.

One of the main reasons the plague had such devastating consequences in the 14th century was the living conditions of the time. Streets accumulated waste and food scraps, creating ideal conditions for black rat nests—and, consequently, for fleas. People lived in close proximity to one another, and merchants on ships spent months in extremely cramped quarters. Today, living conditions in most parts of the world are far better.

However, it is important to understand that the plague is not a disease of the past. It remains endemic in rodent populations across Africa, Asia, South America, and even parts of the United States. Human cases are still detected annually; for instance, an average of seven cases of plague are reported in the US each year. Localized outbreaks occur sporadically in some parts of the world, with instances of human-to-human transmission of pneumonic plague also being recorded.