A woman has died of plague in Russia's remote Irkutsk region in Siberia, Alexei Tsydenov, governor of the neighbouring region of Buryatia, said in a social media post on Friday.
That is close to the entirety of what is known.
Tsydenov governs an adjoining region and not the one with jurisdiction over the case. Russia's health ministry had not issued any statement, AFP reported, adding that it was unable to verify what else has been published about the death.
But Russian media outlets have named the woman as a 28-year-old laboratory technician, reported that she worked at the Irkutsk Anti-Plague Institute, and said she may have contracted pneumonic plague after a test tube broke. Around 200 of her contacts have been placed under quarantine since then, the reports say.
Russian authorities have not confirmed the details, and the route of her infection remains unestablished.
A look at the history of plague and why a single death in Siberia is being watched closely:
The plague
Plague is caused by Yersinia pestis, a bacterium that circulates naturally in small mammals and their fleas, the World Health Organization (WHO) says. People are infected through the bite of an infected flea, direct contact with infected tissue, or the inhalation of infected respiratory droplets.
{{/usCountry}}Plague is caused by Yersinia pestis, a bacterium that circulates naturally in small mammals and their fleas, the World Health Organization (WHO) says. People are infected through the bite of an infected flea, direct contact with infected tissue, or the inhalation of infected respiratory droplets.
{{/usCountry}}It takes three forms. Bubonic plague, the most common, produces the painful swollen lymph nodes known as buboes. Septicaemic plague attacks the bloodstream. And pneumonic plague infects the lungs and is the only form that passes directly between people through the air.
Bubonic plague is the form most often seen, and its case-fatality ratio – according to WHO – is at 30% to 60% without treatment. Pneumonic plague is far rarer, but WHO says it is fatal unless treated early. Antibiotics work, which makes diagnosis within hours rather than days the decisive factor.
The contagiousness of the pneumonic form makes the Irkutsk case, if confirmed, worrying. Its capacity to spread was documented during the Manchurian outbreak of 1910-11, which killed tens of thousands of people, according to a consensus statement on plague as a biological weapon published in the Journal of the American Medical Association in 2000.
It also makes news because it comes nearly seven years after a novel virus, Sars-CoV-2, produced a pandemic that shaped the first quarter of this century.
Plague, though, is now a treatable bacterial infection, and those exposed to a case can be given antibiotics preventively too. Transmission of the pneumonic form also requires close contact with an infected person's respiratory droplets, which is why the response to a single case is likely to be the identification and observation of contacts rather than population-wide restriction.
Nonetheless, plague has never been eradicated world over. WHO lists the Democratic Republic of the Congo, Madagascar and Peru as the three most endemic countries. The United Nations body also recorded 3,248 cases worldwide, including 584 deaths, between 2010 and 2015.
A study in the US Centers for Disease Control and Prevention's peer-reviewed journal Emerging Infectious Diseases found that the DRC accounted for 54% of plague cases declared worldwide between 2004 and 2014. Madagascar experienced a large urban pneumonic outbreak in 2017.
Southern Siberia and Mongolia hold natural plague reservoirs in marmot populations. So, a plague death in Irkutsk is not completely anomalous.
Also read: The science of H1N1, the surge in Delhi and how it differs from Covid-19
Three pandemics
The Justinianic plague of the sixth century was the first documented pandemic caused by plague, and the bacterium has produced two more since. Named after the Byzantine emperor in whose reign it struck, it was identified as the work of Y. pestis only recently. Researchers, writing in The Lancet Infectious Diseases in 2014, reconstructed the bacterium's genome from the teeth of two people buried at Aschheim in Bavaria, Germany. The strain they found is now believed to be extinct.
The second was the Black Death of 1346 to 1353, and its origin was established only recently. Researchers led by Maria Spyrou and Johannes Krause of Germany's Max Planck Institute for Evolutionary Anthropology, writing in Nature in June 2022, analysed ancient DNA from seven people buried at the Kara-Djigach and Burana cemeteries in the Chüy Valley of modern Kyrgyzstan, near Lake Issyk-Kul. Tombstones at the sites, dated directly to 1338 and 1339, give the cause of death as "pestilence". Plague DNA was present in three of the seven samples, and the team concluded that the evidence supports an early fourteenth-century source for the second pandemic in central Eurasia.
The third began in Yunnan in southwest China in the mid-nineteenth century, reached Hong Kong in 1894 and was carried by rat-infested steamships to port cities on every inhabited continent, killing millions in just India and China. The pandemic is generally treated as having run its course by about 1960, by which point annual deaths worldwide had fallen to a couple of hundred.
The bacterium, from this plague, has continued to survive in rodent populations in the Americas, southern Africa and Madagascar, which is why the disease remains endemic in some regions till date.
Over centuries, the plague shaped how Europe learned to write about authority and quarantine. The fourteenth-century Florentine writer Giovanni Boccaccio set his book Decameron among characters fleeing the Black Death. Daniel Defoe reconstructed London's epidemic of 1665 in A Journal of the Plague Year, published in 1722. Albert Camus used a plague-stricken Oran in his 1947 novel, The Plague, to write about occupation, complicity and the obligation to tell the truth about an outbreak.
Much of this literature was about official conduct against the backdrop of people afflicted with disease.
Also read: Covid-19 forced vulnerable Indian households into ‘impossible choices’: Study
The plague in India
Waldemar Haffkine, a bacteriologist who had developed a cholera vaccine, came to Bombay at the outbreak of the plague epidemic in October 1896 and produced the world's first plague vaccine, working from a Plague Research Laboratory housed in a building provided by Aga Khan, according to the US National Library of Medicine's record of his papers. The laboratory later moved to Parel, and it operates today as the Haffkine Institute for Training, Research and Testing under the Maharashtra government.
Outbreaks of bubonic and pneumonic plague also began in India in August 1994, with 693 suspected cases and 56 deaths conveyed to the WHO, most of them in Surat. The Surat outbreak also triggered panic, prompting hundreds of thousands to flee the Gujarat city as reports of first diagnosis and deaths emerged.
Laboratory accidents
Russia does not use the biosafety level scale familiar from Western laboratories. It classifies pathogens into groups, which are governed by specific rules for handling and licensed by Rospotrebnadzor, the consumer and public health watchdog, according to a presentation by Russia's Research Anti-Plague Institute 'Microbe' to a United Nations meeting. Anti-plague institutes work with live virulent strains.
An accident in Irkutsk isn't established but laboratory-acquired infections with dangerous pathogens have been recorded across the globe in the past.
In Chicago in 2009, a university geneticist died after exposure to a weakened strain of Y pestis, which had not been known before to cause laboratory infections or deaths in people. Investigation into the death determined that the cause was likely an unrecognised occupational exposure leading to septic shock. A postmortem diagnosis of hereditary haemochromatosis, a condition causing iron overload, was also made. The US CDC said one possible explanation was that the excess iron allowed the weakened strain to become virulent.
In Birmingham in 1978, a medical photographer at the University of Birmingham Medical School died of smallpox, roughly a year after the last naturally acquired case anywhere in the world. The official UK inquiry led by the microbiologist Reginald Shooter concluded that the virus most likely travelled through a poorly maintained service duct from a laboratory on the floor below. Expert evidence produced at a subsequent prosecution disputed that route. How she was infected has not been established.
In Sverdlovsk, now Yekaterinburg, in 1979, an anthrax outbreak killed at least 66 people. Soviet authorities attributed it to contaminated meat. A team led by the Harvard geneticist Matthew Meselson, publishing in Science in November 1994 after on-site investigations, concluded that the outbreak was caused by the escape of an aerosol of anthrax pathogen from a military facility. Russian president Boris Yeltsin, who was the Communist Party chief in Sverdlovsk at the time of the outbreak, acknowledged the accident in 1992, 13 years after the event.
Also read: Billions of doses later, a Lancet review confirms mRNA vaccine safety
Why one death draws this much attention
The scrutiny to this case comes years after the Covid-19 pandemic, whose origin remains disputed. One side holds that Sars-CoV-2 passed to people from animals sold in a Wuhan market in China. The other holds that it escaped from a laboratory in the same city, most often named as the Wuhan Institute of Virology, which studied coronaviruses.
The question hasn't been settled till date.
US's Central Intelligence Agency (CIA) said in January 2025 it assesses with low confidence that a research-related origin is more likely than a natural origin, but it added that it was continuing to assess that both scenarios remain plausible. The US Department of Energy had earlier reached a similar conclusion, also with low confidence.
Chinese authorities have dismissed the question as unhelpful and politically motivated.
There have also been published papers pointing the other way.
Two papers in Science in July 2022, one led by Michael Worobey of the University of Arizona and the other by Jonathan Pekar, then at the University of California San Diego, concluded that the Huanan Seafood Wholesale Market in Wuhan was the early epicentre of the outbreak. Researchers said there was insufficient evidence to define the events that led to the virus reaching the market in the first place, but that its analyses indicated the virus emerged through the live wildlife trade. A 2024 paper in Cell reached a similar conclusion after genetic analysis of the market samples.
Those findings have since been contested, including in a critique published in the journal National Science Review and in correspondence to Science, with scientists questioning the statistical basis for calling the market an epicentre rather than an amplifier.
Nearly seven years of that argument have not yielded any agreed method for distinguishing a natural outbreak from an accidental one.