Around July and August of 2016 in a remote corner of Siberia called the Yamal Penninsula, more than 2,000 reindeer unexpectedly perished. Initially, a heat wave was suspected to have caused heatstroke in the reindeer, but doctors soon realized they had also become infected by bacillus anthracis, the bacterium responsible for anthrax. (Yes, the same anthrax that gained notoriety after being sent in powdered form to United States senators in 2001.) The Siberian anthrax outbreak also caused the hospitalization of more than 20 people and even one death.
But anthrax had not been seen in Siberia since 1941 so was this a case of bioterrorism? Fortunately not, but the suspected cause is also troubling. Researchers believe the unusually high temperatures during the heat wave caused the permanently frozen soil – called permafrost – to thaw, releasing formerly frozen spores of anthrax into the air in a case of science fiction playing out in reality.
During the last anthrax outbreak in the region 75 years ago, the bodies of reindeer who succumbed to the infection were buried. However, the frozen nature of the tundra means that bodies cannot easily be buried too deeply beneath the surface. The cold, dark, low oxygen conditions of the permafrost also mean that certain bacteria can exist for long periods of time, laying dormant until they are re-released by, for example, the melting of the soil by a heat wave.
Could other diseases be “reanimated”?
With average temperatures rising across the globe, and rising as much as 2-3 times faster in the Arctic, is the Siberian anthrax outbreak an omen for future reanimated “zombie” diseases? In the Arctic, permafrost can extend over 1000 feet deep in some places and some of those deeper layers can be as old as thousands or even millions of years suggesting a plethora of diseases, some that possibly even pre-date humankind, may be buried there. (From personal experience, I can tell you that the term “Pandora’s box” comes up frequently when reading articles on the subject.)
However, the authors of those articles also point out that anthrax is well-suited for post-thaw reanimation because it forms spores, a method of reproduction designed to withstand harsh conditions, like frozen tundra, for long periods of time. Other bacteria that form spores include Clostridium tetani, responsible for tetanus, and Clostridium botulinum, responsible for botulism, although there are so far no cases of those infections being thawed and reactivated.
Past outbreaks suggest that small pox and bubonic plague likely lurk beneath the frozen surface in Siberia. In an effort to better understand the disease, virologists have reconstructed the Spanish flu from lung tissue preserved in bodies buried in mass graves in the Alaskan village of Brevig Mission over 100 years ago. In 1918, the Spanish flu virus killed between 20 to 50 million people, and infected about one fifth of the world’s population, including 90% of the residents of Brevig Mission.
There have been several other lab experiments that have successfully reanimated different strains of bacteria. In 2005, scientists revived a strain of bacteria found buried in ice from the Pleistocene, or the Ice Age, interned in a frozen tunnel in Alaska since the time wooly mammoths roamed the Earth. Another study found bacteria in 8-million-year-old Antarctic ice although its metabolic activity was found to be compromised by its long stay in the ice. Scientists have even found strains of an ancient, antibiotic-resistant bacteria in an underground cave system in Carlsbad, New Mexico that hadn’t had contact with the surface in over 4 Myr.
A 2014 study resulted in the successful revival of two “giant” viruses – so-called because, unlike most viruses, they are so large that they can be seen with an ordinary microscope – buried only 100 feet below the Siberian surface. Those particular giant viruses only affect single-celled amoeba but the authors of the study are careful to note that their success “suggests that the thawing of permafrost either from global warming or industrial exploitation of circumpolar regions might not be exempt from future threats to human or animal health.”
This warning highlights another way global warming could lead to the release of diseases from ancient ice. As Arctic ice melts, previously inaccessible pathways become suddenly passable, and industries are already looking to mine for gold and other minerals as well as drill for oil.
Climate change, of course, also brings with it other concerns over the spread of diseases.
Will these frozen diseases eventually affect humans?
The fact that these viruses can be reanimated under highly controlled lab conditions, however, does not mean that we will see the return of now dormant diseases in nature. What these results do suggest is that the chances of that happening are at least nonzero. Climate change, of course, also brings with it other concerns over the spread of diseases. Along with rising temperatures comes the expansion of the geographic span of climates where disease carriers (like mosquitos or ticks) as well as their food sources can thrive.
So while we may not fully understand yet what climate change has in store for us in the way of diseases, further investigation into the potential for the revival of long buried bacteria, particularly strains that are resistant to our antibiotics, would help us be better prepared for the rising temperatures to come.
Until next time, this is Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science.