Pneumonic Plague: How Likely Is It to Spread Globally Like COVID?
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This might feel strangely familiar or like something seen before.
Last Friday in Siberia, a woman died of pneumonia due to ‘unknown’ causes; it is suspected that her body may have been exposed to plague-causing bacteria, the pathogen behind epidemics.
According to Russian media, about 200 people were then placed in isolation.
Officials have tried not to show concern over the matter, but various speculations and fears have spread on online platforms.
The 28-year-old woman named Darya Shipilova worked at the Anti-Plague Institute in the Irkutsk region of Siberia.
Unofficial reports suggest that she developed pneumonia-like symptoms after either a test tube containing the plague bacterium broke or due to a visit to the Buryatia region near the Mongolian border.
Plague infections are known to occur in wild animals in that area.
The official cause of Shipilova’s death has not yet been confirmed; tests are ongoing.
However, one thing is clear. Experts say the likelihood of this developing into a global pandemic is low. Here’s why.
Types and Variations of Plague
Plague is caused by the bacterium Yersinia pestis. Medically, it is classified into three types: bubonic plague, pneumonic plague, and septicemic plague.
Bubonic plague is the most common form. It spreads through the bite of infected fleas. Once in the body, the bacteria reach the lymph nodes and cause painful swellings known as ‘buboes’ typically in the groin, neck, and armpits.
Bubonic plague rarely spreads from person to person. However, if it spreads to the bloodstream, it can cause septicemic plague; if it reaches the lungs, it can develop into pneumonic plague.
Pneumonic plague is different from other types because it can transmit directly between humans through tiny droplets released when an infected person coughs or sneezes.
If untreated, pneumonic plague is usually fatal. Symptoms can appear in less than 24 hours after infection.
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During the 14th century in Europe, the ‘Black Death’ pandemic caused by bubonic and pneumonic plague killed more than 250 million people.
It wiped out approximately one-third to two-thirds of Europe’s population. The spread was facilitated by open trade routes and importation of grain and flour via ships.
Risk Assessment
However, modern conditions are not favorable for rapid spread of the plague.
Firstly, while untreated pneumonic plague is often fatal, these diseases can now be easily treated with commonly available antibiotics.
“We have two effective therapies available for treating bubonic plague,” says Professor Piero Olliaro, an infectious diseases and poverty specialist at Oxford University.
In 2025, he published results from the first randomized controlled trial for bubonic plague treatment conducted in Madagascar.
The study showed oral ciprofloxacin and injected aminoglycoside antibiotics to be 91% and 92% effective respectively in treating bubonic plague.
Even among a small number of patients infected with pneumonic plague, prompt treatment led to an 85% survival rate.
Another reason plague is unlikely to become a global pandemic is that pneumonic plague only spreads after symptoms appear.
Symptoms usually manifest clearly and severely within 24 hours, enabling rapid isolation and treatment of infected individuals.
“The absence of warnings doesn’t mean pathogens are moving by air travel undetected or that new infections are spreading,” explains Associate Professor Jania Stamataki, a viral immunologist at the University of Birmingham.
According to her, such a situation would reveal itself quickly and clearly.
How Much Vigilance Is Needed?
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The World Health Organization (WHO) is tracking and monitoring all individuals who had contact with infected persons, and so far, no symptoms have been reported in any of them.
This step follows recommendations by the US Centers for Disease Control and Prevention.
The agency suggests identifying at-risk individuals for surveillance, testing, quarantine, and making antibiotics available.
WHO spokesperson Christian Lindmayr released an initial risk assessment on Tuesday.
He told reporters, “The risk in Irkutsk is moderate to low, the overall risk for the Russian Federation is low, and for the WHO European region, the risk is very low.”
Can It Spread from Laboratories?
Infections spreading from laboratory environments are extremely rare due to strict safety protocols.
“These are highly specialized labs,” says Stamataki. “There are many layers of security here.”
Researchers wear full personal protective equipment and handle samples only inside a biosafety cabinet. The cabinet maintains negative air pressure to prevent outside air entering and protect users.
“Even if a test tube breaks, it will break inside the cabinet, keeping users safe,” she explains.
Samples are placed in secure outer containers, and technicians receive rigorous training before working in the lab.
In the 14th century, the rapid spread of plague was mainly due to poor living conditions, accumulated refuse in streets, and food waste that attracted black rats and fleas.
Close human living quarters and long, cramped ship voyages by traders further enhanced the spread. Such conditions are largely absent in many parts of the world today.
But it is important to understand that plague is not merely a disease of history.
Outbreaks of plague in rodent populations continue to occur in Africa, Asia, South America, and the United States among other places.
Each year, a number of human plague cases are confirmed; for instance, an average of seven cases annually occur in the US.
Occasionally, localized epidemics happen in some areas where pneumonic plague spreads person-to-person.
In 2017, Madagascar experienced an outbreak with 2,417 cases and 209 deaths.
Olliaro notes that plague outbreaks generally remain geographically limited, indicating recovery from epidemics. They typically do not develop into global pandemics.
While the pandemic potential is low, investment in plague treatment and prevention is necessary.
“It may not affect many globally, but its impact is certainly real,” says Olliaro. “It is an important disease and we must never forget its existence.”