Zombie Pathogens!

Author: Semon Randall, Edited by: Emilyann Ashford

Rising global temperatures are resurrecting dormant pathogens from permafrost

Figure 1. Permafrost map of the North and South Pole Source

Figure 1. Permafrost map of the North and South Pole Source

What are pathogens and why are they in permafrost?

Pathogens are any microorganism or virus that can cause disease (1). When pathogens face stressful conditions such as nutrient depletion or extreme temperature changes, they go into a state of reduced metabolic activity or dormancy. Once these conditions become optimal again the pathogens can remerge to replicate and infect humans (2). Although dormant pathogens are ubiquitous in nature, areas that are cold, stable in temperature, absent of light and neutral in pH are perfect conditions for pathogen preservation. Therefore, permafrost layers are home to billions of century-old dormant pathogens. Permafrost is an impermeable layer of soil that remains frozen and covers a little less than a fifth of the Earth’s surface (Fig 1).

Figure 2. Mean annual permafrost temperatures from 1978 – 2016. The colors and numbers of graph A show the distinct location of temperature collection. Graph b shows the corresponding temperature changes at that location. Source

Figure 2. Mean annual permafrost temperatures from 1978 – 2016. The colors and numbers of graph A show the distinct location of temperature collection. Graph b shows the corresponding temperature changes at that location. Source

What are the risks associated with the thawing of permafrost?

According to the Global Network of Permafrost Test Sites, permafrost regions around the world have warmed by, on average, half a degree Fahrenheit between 2007 and 2016 (Fig. 2) (3). Due to global warming, permafrost layers have the potential to thaw and release bacteria and/or viruses into adjacent streams and soil. This was the case in Siberia, where a heat wave, in 2016, thawed the permafrost layers and there with it, a reindeer carcass infected with Bacillus anthracis, the causative agent of anthrax (4) was also thawed. Scientists hypothesized that the carcass released infectious spores into the soil and water in the Yamal Peninsula which subsequently led to the death of one child. In addition, a dozen people in the region were infected along with approximately 2,000 reindeer. This was an alarming outbreak because the USSR had officially declared itself “anthrax-free” in 1968 (5). In addition, evolutionary biologists, Jean-Michel Claverie and Chantal Abergel successfully thawed and cultured a giant virus that was buried in Siberian permafrost for over 30,000 years (Fig. 3) (6). Although the virus, Pithovirus sibericum, was found to be only infectious in amoebas, the discovery further raised the alarm on the potential risks associated with thawing permafrost. 

Figure 3. Pithovirus sibericum, the virus that was revived in a laboratory in France Source

Figure 3. Pithovirus sibericum, the virus that was revived in a laboratory in France Source

What other deadly pathogens hide in the permafrost?

As a consequence of permafrost melting, vectors of deadly infections of the 18th and 19th centuries can return, especially near the cemeteries where the victims of these infections were buried. For example, during the Smallpox epidemic in the 1980’s, bodies were buried under the upper layer of permafrost on the banks of the Kolyma River in Siberia. After 120 years, bodies were recovered that had sores characteristic of the marks left by smallpox [7]. Although no traces of the smallpox virus itself was detected, fragments of the smallpox DNA were recovered. Additionally, diseases such as the plague which wiped out tens of millions of people in the Middle Ages, could be another virus found in the corpses buried in the permafrost. 

What can we do to stop this pathogenic zombie apocalypse?

The increased rate of melting permafrost can raise concerns regarding the resurrection of many deadly diseases and pathogens. To help reduce the rate of permafrost thawing, we must reduce greenhouse gas emissions. Greenhouse gas emissions can be reduced locally by using solar energy, reducing your use of electricity and using less hot water. In addition, paleontological excavations in permafrost layers must be done using proper personal protective equipment (PPE) in order to reduce the risk of exposure to potential pathogens. For more information on climate solutions, please visit the Center for Climate and Energy Solutions.

Citations

  1. Pirofski, La., Casadevall, A. Q&A: What is a pathogen? A question that begs the point. BMC Biol 10, 6 (2012). https://doi.org/10.1186/1741-7007-10-6

  2. Rittershaus, Emily S.C., et al. “The Normalcy of Dormancy: Common Themes in Microbial Quiescence.” Cell Host & Microbe, vol. 13, no. 6, 2013, pp. 643–651., doi:10.1016/j.chom.2013.05.012.

  3. Burgess, M, et al. “Global Terrestrial Network for Permafrost (GTNet-P): Permafrost Monitoring Contributing to Global Climate Observations.” 2000, doi:10.4095/211621.

  4. Doucleff, Michaeleen. “Anthrax Outbreak In Russia Thought To Be Result Of Thawing Permafrost.”NPR, NPR, 4 Aug. 2016, www.npr.org/sections/goatsandsoda/2016/08/03/488400947/anthrax-outbreak-in-russia-thought-to-be-result-of-thawing-permafrost.

  5. Parkinson, Alan J., et al. “Climate Change and Infectious Diseases in the Arctic: Establishment of a Circumpolar Working Group.” International Journal of Circumpolar Health, vol. 73, no. 1, 2014, p. 25163., doi:10.3402/ijch.v73.25163.

  6. Legendre, M., et al. “Thirty-Thousand-Year-Old Distant Relative of Giant Icosahedral DNA Viruses with a Pandoravirus Morphology.” Proceedings of the National Academy of Sciences, vol. 111, no. 11, 2014, pp. 4274–4279., doi:10.1073/pnas.1320670111.

  7. Fox-Skelly, Jasmin. “Earth - There Are Diseases Hidden in Ice, and They Are Waking Up.” BBC, BBC, 4 May 2017, www.bbc.com/earth/story/20170504-there-are-diseases-hidden-in-ice-and-they-are-waking-up. 

Emilyann Autumn