Scientifically Speaking | Will the next killer disease originate in the Arctic?
The Earth faces a looming crisis. Globally, temperatures are rising. Heatwaves, droughts, ocean acidification, and rising sea levels are on the horizon. Around 90% of the world lives in the northern hemisphere with major population centres in the tropical and subtropical regions. These regions will be severely affected.
However, local effects are not equal. In the Arctic, temperatures are rising twice as fast in other parts of the world. As a result, the thick layer of soil called permafrost that has remained frozen throughout the year is thawing. The thawing of permafrost will worsen the effects of the climate crisis, because stored carbon will be released in the process. Likewise, the loss of sea ice and ice sheets covering land will accelerate the rise in temperatures. White ice reflects sunlight keeping the planet cooler, whereas darker seawater absorbs heat.
Increase of average temperatures is modifying the environment in other ways too. There is already evidence that diseases that have typically afflicted the equatorial belt are spreading up into higher latitudes. Mosquitoes, ticks, and other insects spread many of these diseases.
The West Nile virus causes hundreds of deaths every year in the United States, where it was first reported in 1999. The spread of this viral disease is dependent on the life cycle of mosquitoes. With rising temperatures, West Nile will become more prevalent in Canada, including parts of the Arctic. It is only a matter of time.
Warming temperatures are also causing changes in the habitats of wild birds such as ducks and geese that can carry avian flu. Earlier this year, Russia reported the first case of the H5N8 avian flu passing from birds to humans. Changes in habitats of other wild animals such as foxes might also increase the geographic distribution of rabies.
Scientists are also concerned about the rise of viruses and bacteria from thawing permafrost and ice. In the summer of 2016, there was an outbreak of anthrax in a remote part of Siberia. Dozens of people were infected, and a young boy was killed. Around 2,300 reindeer perished in the outbreak. Anthrax is a serious infectious disease caused by bacteria that can remain dormant as spores. Spores of anthrax can remain viable for at least a few decades in frozen soil and ice. A plausible idea of how the outbreak started is that record temperatures that year caused a frozen reindeer carcass infected with anthrax spores to thaw. And as carcasses of other animals (including those of extinct mammoths) thaw, we might see more disease outbreaks.
Another concern is the emergence of viruses and bacteria with the potential to cause epidemics. These disease-causing microbes might be dormant for hundreds or even thousands of years. Genetic material from the H1N1 influenza virus that caused the Spanish Flu pandemic of 1918, as well as that of smallpox have been recovered from permafrost. The reemergence of a virus like smallpox (which is the only human disease to have been eradicated) would be disturbing since humans are no longer routinely vaccinated.
In the case of H1N1, researchers found a well-preserved body of an infected person in Alaska. In 2005, Jeffery Taubenberger used samples from this person to reconstruct the genome of the lethal H1N1 virus. This viral sequences obtained from the deceased person were not capable of infecting others, but that does not have to be the case.
In fact, we have ample evidence that infectious viruses and bacteria can be resurrected from frozen ice, soil, animal carcasses, and human corpses. In 2014, researchers reported the discovery of giant viruses that had been dormant in Siberian permafrost for around 30,000 years. These particular viruses were not harmful to humans, but they infected amoeba. The following year, bacteria were recovered from Alaskan permafrost. These bacteria had also been dormant for thousands of years.
These conditions are not restricted to the Arctic alone either. Glacial ice that has persisted for thousands of years is melting. Last month, researchers published a paper in the journal Microbiome reporting 15,000-year-old-viruses (including 28 different kinds identified for the first time) that they found in glacial ice from the Tibetan Plateau.
Taken together, these studies show that some viruses and bacteria can survive for thousands of years in permafrost and ice, and that the potential for some of them to infect humans is real. To be clear, the chances of an epidemic originating from microbes originating from permafrost or ice is low. But as the Covid-19 pandemic has demonstrated, even low probability events with major consequences need to be taken seriously.
Anirban Mahapatra, a microbiologist by training, is the author of COVID-19: Separating Fact From Fiction
The views expressed are personal