Getty ImagesA Russian lab technician has died at a plague research centre in Siberia, but there are many reasons pneumonic plague is usually easily contained.
It may seem eerily familiar.
On Friday last week, a woman died from pneumonia of “undetermined” origin in Siberia after potentially being exposed to the plague. Russian media have reported that nearly 200 people were placed in isolation. Officials quickly shut down concern, but online speculation and alarm have been spreading.
The 28-year-old woman, named Darya Shipilova, worked at the Anti-Plague Institute in Siberia’s Irkutsk region. Unconfirmed reports suggested the woman fell ill with pneumonia-like symptoms either after breaking a test tube containing the plague bacterium, or following a field trip to the Buryatia region on the border with Mongolia. In this area, plague is endemic among wild animals.
The plague is caused by the bacterium Yersinia pestis. Clinically there are three forms: bubonic plague, pneumonic plague and septicaemic plague.
The bubonic plague is the most common variant and is spread by the bites of infected fleas. Once inside a human host, the bacterium travels to the lymph nodes where it causes painful sores called ‘buboes’ in the groin, neck and armpits. Human-to-human transmission of bubonic plague is rare, but the bacterium can spread to the blood where it causes septicaemic plague, or the lungs, causing pneumonic plague.
Unlike the other forms of plague, the pneumonic version can pass from person to person via tiny droplets released into the air when a person coughs or sneezes. Pneumonic plague is also usually fatal unless treated early, and the time from exposure to when symptoms begin can be as short as 24 hours.
The Black Death, caused by bubonic and pneumonic plague, killed more than 25 million people in Europe in the 14th Century, wiping out between one third to two thirds of the population. It was made possible by newly opened trade routes, and the importing of goods such as grain and flour via ships.
However, modern conditions are much less hospitable for the spread of the plague.
Firstly, while the pneumonic version of Yersinia pestis is nearly always fatal if left untreated, today it can be overcome with simple, widely available antibiotics.
“We have two treatments that work very well for bubonic plague,” says Piero Olliaro, professor of poverty-related infectious diseases at the University of Oxford.
The bioterrorism threat
Health authorities including the US Center for Disease Control and Prevention have plans for how to respond if the plague is released intentionally. This includes tracing contacts, providing guidance to hospitals, and sourcing medical supplies. The risk is considered low, but the plague has been used as a weapon before. Anecdotal reports suggest infected corpses were thrown at enemies in the 14th Century, and the Japanese military dropped infected fleas on Chinese civilians during World War Two.
In 2025, Olliaro and colleagues published the first ever randomised, controlled trial for the treatment of bubonic plague in Madagascar. It showed that two antibiotics – oral ciprofloxacin and injectable aminoglycoside – were 91% and 92% effective at treating bubonic plague, respectively. Even in the handful of cases where a person’s plague became pneumonic, 85% of people got better and survived with swift treatment.
Another reason that a plague pandemic is very unlikely is that, unlike the Covid-19 virus, pneumonic plague can only be spread after symptoms begin. This is usually within 24 hours. Symptoms are severe and obvious. This means that any further cases can be quickly identified, isolated and treated before transmission occurs.
“It’s not something that we can miss, where we would see people getting on a plane and travelling around and seeing new infections everywhere ,” says Zania Stamataki, associate professor of viral immunology at the University of Birmingham. It would be quite obvious, quite quickly, she says.
According to the World Health Organisation, all the patients’ contacts have reportedly been identified and are being monitored, with none showing symptoms of illness currently. This action is in line with public health advice given by the US Center for Disease Control, which recommends identifying persons considered at risk so that they can be monitored, screened, quarantined and given antibiotics.
Getty ImagesChristian Lindmeier, spokesperson for the World Health Organisation, announced the organisation’s initial risk assessment on Tuesday. It’s “moderate to low for Irkutsk, a low risk for the Russian Federation as a whole and very low for the WHO European region”, he told reporters.
Generally speaking, transmission in a laboratory environment is an extremely rare event, as rigorous protocols are usually in place to prevent accidental exposure. “These are very specialised labs,” says Stamataki. “There are layers and layers of protection.”
For instance, Stamataki explains that researchers wear full personal protection equipment (PPE). Samples are also only handled within biosafety cabinets. These safety cabinets are under negative air pressure, which means that the flow of air goes inwards and away from the user. “If a tube breaks, it would break inside the cabinet, and the user would be protected,” she says.
Even when you are transporting a tube, the tube is housed in a secondary containment vessel, explains Stamataki. Technicians also undergo vigorous training before working in such laboratories, she says.
One of the main reasons that plague spread so rapidly in the 14th Century is the generally poor living conditions at that time. Waste and food scraps littered the streets, creating ideal nesting grounds for the black rats that carried the disease-bearing fleas. People lived in very close proximity to one another, and traders spent months in cramped ships. These conditions no longer exist for much of the world.
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Nevertheless, it’s important to state that the plague isn’t just a historical disease. Plague is endemic in rodent populations in Africa, Asia, South America and even the US.
Every year there are cases in humans too. In the US, for example, an average of seven human plague cases are reported each year. In some parts of the world, there are also sometimes local outbreaks where human to human transmission of pneumonic plague occurs.
In 2017, an outbreak in Madagascar led to 2,417 cases of the plague and 209 deaths. However, Olliaro points out that the fact that this ended is evidence that plague outbreaks tend to be confined. They don’t usually lead to a pandemic.
However, while an outbreak of the plague is unlikely to achieve truly global spread, this doesn’t mean that we shouldn’t invest in treating and preventing plague.
“It may not impact many people on the global scale, but it still causes suffering,” says Olliaro. “It is an important disease, and so we should not forget that plague exists.”
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