The unexplained death this month of a Russian lab technician at a Siberian facility for the study of dangerous pathogens raised global anxieties over the potential for an outbreak of pneumonic plague.
But while the cause of concern — bound up in a lack of transparency from Moscow — was new, Russia’s frozen hinterlands have long been the source of a separate fear that they could harbor disease risks for which the world is not prepared.
Russian authorities imposed containment measures after the 28-year-old’s death from what they said was pneumonia of “unknown origins,” prompting the United States to ask for more information. A World Health Organization report released Saturday said that Russian authorities found no signs of an outbreak of plague or some other infectious disease, but did not provide sufficient details to identify the origin of the woman’s illness or say whether exposure at work played a role in it.
Siberia’s vast wilderness harbors natural reservoirs of pathogens, from fleas that spread plague found in marmots and squirrels to ticks bearing encephalitis to the ancient pathogens frozen in the layer of permafrost.
The Russian institute where the lab technician worked was set up in the 1930s as a plague prevention station to curb outbreaks of the deadly bacterial disease that periodically affected local populations as well as people in neighboring Mongolia and China’s Manchuria region. The disease, for which early antibiotic treatments were pioneered that decade, could be spread through contact with marmots, which were hunted for meat and sometimes eaten undercooked or even raw, like in a 2019 case of a Mongolian couple.
The settlement of Siberia, which had a 19th-century gold rush and served as a place of exile for criminals under the Russian Empire, connected the remote region to the western parts of the empire and raised the risk of plague spreading farther west, much as epidemic diseases from European Russia, such as cholera and typhus, easily reached Siberia through migrating workers and because of the near-total absence of medical care.
A study published this year suggested that the bands of hunter-gatherers who inhabited the Lake Baikal region were the victims of the earliest known plague outbreak, about 5,500 years ago. To this day, plague remains endemic in parts of Siberia and the Russian Far East, where the bacterium persists naturally among wild rodents.
Human cases in Russia are rare, however. The country’s last recorded human infection was in 2016, when a 10-year-old boy in the Altai region contracted plague after contact with a marmot.
The threat of dangerous disease comes not only from wildlife but also from the millennia-old microbes and viruses stored in the permafrost that underlies the vast majority of the region.
About a decade ago, a group of researchers isolated “zombie viruses” from Siberian permafrost, raising fears that a new global medical emergency could be triggered by a disease from the distant past.
The permafrost, a dark, cold, oxygenless mass, is a perfect storage container for biological material, and scientists believe that at its deepest levels it may contain viruses up to a million years old, far older than Homo sapiens, the modern human species.
In 2023, the researchers — led by Jean-Michel Claverie of Aix-Marseille University in France — published a landmark study in the journal Viruses documenting the revival of ancient viruses from the Siberian permafrost.
The report warned that accelerating permafrost thaw caused by climate change poses a potential public health threat by releasing dormant pathogens. Claverie’s team isolated 13 ancient viruses taken from locations across Siberia, belonging to five new viral groups. The oldest, a Pandoravirus yedoma, had been frozen solid beneath an underground lake for 48,500 years, while other, younger strains (around 27,000 years old) were extracted from the remains of a woolly mammoth’s stomach and from mammoth wool.
Other researchers have noted that although the revived viruses were able to infect amoebas in lab conditions, it is unclear whether such viruses could infect animals or humans, or find a host outside a controlled laboratory.
Claverie and his team cautioned at the time that unknowns remain buried in the permafrost, and a warming climate, which would also open previously untouched lands to deeper development, could expose people to pathogens that affect humans.
In 2016, climate change played a role in unleashing anthrax in the remote Yamalo-Nenets region of Siberia, experts said at the time. Unusually high temperatures that summer, soaring to 95 degrees Fahrenheit, melted permafrost, and according to one hypothesis, exposed an infected reindeer carcass. The pathogen spread to living reindeer and eventually to a community of nomadic herders, where a 12-year-old boy died.
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