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Thawing Permafrost: A Pandora’s Box of Ancient Diseases?

Written by Kristine Yang ’25

Edited by Lizzy Zhang '24

A few months ago, parts of the Arctic Circle reached temperatures warmer than the average Floridian summer [1].

And as this past August saw an alarming 298 cities experience their hottest ever temperatures [2], new figures show that concerns over scorching global heat are only intensified in the Arctic, where the region has been warming at a rate four times faster than the Earth as a whole.

This rapid warming comes at a time when the worldwide death toll for COVID-19 is surpassing 6.5 million [3]. In the Arctic, these two crises may be far more entwined than they appear, and the answer lies in the permafrost.

A thick ground layer of permanently frozen soil and organic matter, permafrost constitutes one quarter of land in the Northern Hemisphere. Within the past 10 years, warming temperatures have caused long-term thawing of the permafrost from the top down – a development which is expected to accelerate over the next few decades [4].

Having gradually accumulated organic material like plants and animal carcasses for thousands of years, permafrost has perfectly preserved disease-causing microorganisms in their frozen state. Due to the thawing, these long-dormant microbes have been awakened and have become exposed near the surface of the ground in what is known as the active layer of permafrost [2].

Once unfrozen, the ancient microbes only pose a public health threat unless they can quickly find a new host to infect.

With the majority of the Arctic Circle being sparsely inhabited by remote indigenous villages, direct human contact with the fresh bacteria and viruses is limited, meaning that the spread of infection from human sources is rather rare [2].

However, with global warming comes new animal migration patterns as moose, for example, are migrating northward for more vegetation [5]. This means herds of potential viral and bacterial hosts are trekking toward a thawed Arctic ground layer harboring fresh disease-causing pathogens. Among these pathogens, strains of smallpox, the 1918 Spanish Flu, and the bubonic plague have all been identified in permafrost samples [6].

Studies show that the chemical structures and stability of these revived microbes indicate the likelihood of reinfection [2]. RNA single-stranded viruses like the 1918 variant of influenza causing the Spanish Flu are chemically fragile and thus are much more unlikely to remain intact after emerging from its frozen state. Conversely, DNA double-stranded viruses like smallpox are a greater cause for concern as their more stable chemical structure allows the complete virus to survive the thawing process.

Revived bacteria diseases remain an elusive threat. While some researchers are dismissive of the threat posed by ancient bacteria due to the accessibility to and abundance of antibiotics, revived infectious bacteria — in conjunction to an emerging antibiotic resistance crisis — has left some researchers hesitant to so quickly reject the premise of a potential ancient bacteria-caused pandemic [2].

Already, in the time that long-term thawing of permafrost began some 10 years ago, revived bacteria from thawed permafrost have caused disease outbreaks in the Arctic and Arctic-adjacent regions.

The most notable case occurred in 2016 after a heat wave struck a remote corner of Siberia called the Yamal Peninsula. As a result, a carcass infected with anthrax from decades earlier had thawed, reviving the infectious bacteria Bacillus anthracis. Reindeer grazing nearby were infected by the revived bacteria and through their movement across the tundra, transmitted the disease to the local population [8].

The outbreak of anthrax – which was previously last recorded in 1941 – killed one person, over 2,300 reindeer, and infected dozens more [6]. The outbreak was so severe that the Russian Federation reversed its policy and began vaccinating animals against anthrax [2].

Infectious microbes preserved in permafrost are incalculable and unpredictable both in their timing and severity. When it comes to permafrost thawing, potential pandemics caused by revived dormant pathogens are not only a real threat, but a threat that multiplies with the acceleration of global warming.



1. Nilsen T. The European Arctic suffers through a heat wave [Internet]. ArcticToday. 2022 [cited 2022 Nov 14]. Available from:

2. Boren Z. The permafrost pandemic: could the melting Arctic release a deadly disease? [Internet]. Unearthed. 2020 [cited 2022 Nov 14]. Available from:

3. Weekly epidemiological update on COVID-19 - 28 September 2022 [Internet]. [cited 2022 Nov 14]. Available from:

4. Wilkerson J. How much worse will thawing Arctic permafrost make climate change? Scientific American [Internet]. By Jordan Wilkerson on August 11 2021 [cited 2022 Nov 14]; Available from:

5. Welch C. Half of all species are on the move—and we’re feeling it. National geographic [Internet]. 2017 Apr 27 [cited 2022 Nov 14]; Available from:

6. European Academies Science Advisory Council; InterAcademy Partnership; National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Division on Earth and Life Studies; Board on Global Health; Board on Life Sciences; Polar Research Board, Everett L. Overview. Washington, D.C., DC: National Academies Press; 2020.

7. Doucleff M. Anthrax outbreak in Russia thought to be result of thawing permafrost. NPR [Internet]. 2016 Aug 3 [cited 2022 Nov 14]; Available from:

8. Liskova EA, Egorova IY, Selyaninov YO, Razheva IV, Gladkova NA, Toropova NN, et al. Reindeer anthrax in the Russian arctic, 2016: Climatic determinants of the outbreak and vaccination effectiveness. Front Vet Sci [Internet]. 2021;8:668420. Available from:


United States National Parks Service Climate Change Response. Thawing permafrost [Internet]. Available from:

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