Pathogens in the Permafrost: Could Melting Ice Unleash Ancient Diseases? (Part 1)

By Deanna Altomara

It’s like a scene from an apocalyptic movie: an ancient virus reemerges from the polar ice caps, unleashing a pandemic that kills millions, causes mass panic, and destroys life as we know it. Some people fear that this is a scenario that could be closer than we think. But do we really have to worry about an epidemic emerging from the icy vaults of pre-history? 

A recent investigation into the frozen landscape of Tibet’s Guliya ice cap unearthed 28 types of never-before-seen viruses–a startling discovery that has reignited the scientific controversy over whether climate change could release “zombie pathogens” from melting permafrost. In this particular study, scientists from the US and China sampled two ice cores from 51 meters under the surface of the Guliya ice cap in the northwestern Tibetan Plateau. The ice samples, which ranged in age from 520 to 15,000 years old, contained 33 distinct viral populations. These viruses were associated with certain bacterial groups, which were probably the main hosts for viral infection. The study was published without undergoing peer-review, so while the preliminary research is fascinating, the results should be taken with caution. 

Permafrost is ice that encases what used to be (think 35,000 years ago) marshy grasslands. Every summer, it partially thaws, and each winter it refreezes, a cycle that has continued for thousands of years. Some microbes can survive near the surface of the permafrost, the partially-thawed area known as the ‘active zone.’ But with climate change, the active zone is pushing deeper into the permafrost, warming up ancient pockets of frozen soil, and also stretching farther north. The permafrost contains frozen soil debris, plants, animals–even perfectly preserved human bodies. One team of scientists even found seeds that had been frozen solid for thousands of years, and still sprouted white blossoms after being warmed and planted.[1] The permafrost harbors a rich archive of the earth’s history, with many examples of organic matter that never decomposed. But as the ice melts, these ancient remnants are beginning to rot, releasing gas into the atmosphere and actually accelerating the process of climate change. 

The threat of a “zombie virus” seemed to become a living nightmare in the summer of 2016, when an anthrax outbreak emerged in Siberia. Anthrax is a disease caused by the bacteria Bacillus anthracis. It lives in soils around the world, where it is occasionally disturbed and triggers deadly outbreaks among both animals and people. In the early twentieth century, over a million reindeer died of anthrax, and were often buried in shallow graves with 7,000 burial grounds across Northern Russia. There was a Russian campaign to vaccinate reindeer, who were most likely to catch the virus and pass it on to humans. This campaign was successful; there were no outbreaks for decades and, assuming that anthrax had been eliminated from the area, deer vaccination stopped in 2007.[2] But anthrax had not disappeared–it was simply hibernating in the permafrost. 

In 2016, an unusually warm summer thawed the permafrost, caused an outbreak of anthrax that killed a twelve-year-old boy and hospitalized dozens more. 

Is this a vision of what is to come? Tune in tomorrow to find out. 

[1] Yashina, S., Gubin, S., Maksimovich, S., Yashina, A., Gakhova, E., & Gilichinsky, D. (2012). Regeneration of whole fertile plants from 30,000-y-old fruit tissue buried in Siberian permafrost. Proceedings of the National Academy of Sciences, 109(10), 4008—4013. doi: 10.1073/pnas.1118386109

[2]  Timofeev, V., Bahtejeva, I., Mironova, R., Titareva, G., Lev, I., Christiany, D., … Vergnaud, G. (2019). Insights from Bacillus anthracis strains isolated from permafrost in the tundra zone of Russia. PloS one, 14(5), e0209140. doi:10.1371/journal.pone.0209140