Throughout history, humans have existed side-by-side with bacteria and viruses. From the bubonic plague to smallpox, we have evolved to resist them, and in response they have developed new ways of infecting us.
We have had antibiotics for almost a century, ever since Alexander Fleming discovered penicillin.
In response, bacteria have responded by evolving antibiotic resistance. The battle is endless: because we spend so much time with pathogens, we sometimes develop a kind of natural stalemate.
However, what would happen if we were suddenly exposed to deadly bacteria and viruses that have been absent for thousands of years, or that we have never met before? Or what if we currently are?
As the Earth warms, more permafrost melts. Under normal circumstances, superficial permafrost layers about 50cm deep melt every summer. But now global warming is gradually exposing older permafrost layers.
Frozen permafrost soil is the perfect place for bacteria and viruses to remain alive for very long periods of time, perhaps as long as a million years. That means melting ice could potentially open a Pandora’s box of diseases.
The temperatures in the Arctic and Antarctica are rising quickly, about three times faster than in the rest of the world. As the ice and permafrost melt, other infectious agents may be released.
“Permafrost is a very good preserver of microbes and viruses, because it is cold, there is no oxygen, and it is dark,” says evolutionary biologist Jean-Michel Claverie at Aix-Marseille University in France. “Pathogenic viruses that can infect humans or animals might be preserved in old permafrost layers, including some that have caused global epidemics in the past.”
In the early 20th Century alone, more than a million reindeer died from anthrax. It is not easy to dig deep graves, so most of these carcasses are buried close to the surface, scattered among 7,000 burial grounds in northern Russia.
However, the big fear is what else is lurking beneath the frozen soil.
People and animals have been buried in permafrost for centuries, so it is conceivable that other infectious agents could be unleashed. For instance, scientists have discovered fragments of RNA from the 1918 Spanish flu virus in corpses buried in mass graves in Alaska’s tundra. Smallpox and the bubonic plague are also likely buried in Siberia.
In a 2011 study, Boris Revich and Marina Podolnaya wrote: “As a consequence of permafrost melting, the vectors of deadly infections of the 18th and 19th Centuries may come back, especially near the cemeteries where the victims of these infections were buried.”
NASA scientists successfully revived bacteria that had been encased in a frozen pond in Alaska for 32,000 years.
For instance, in the 1890s there was a major epidemic of smallpox in Siberia. One town lost up to 40% of its population. Their bodies were buried under the upper layer of permafrost on the banks of the Kolyma River. 120 years later, Kolyma’s floodwaters have started eroding the banks, and the melting of the permafrost has speeded up this erosion process.
In a project that began in the 1990s, scientists from the State Research Center of Virology and Biotechnology in Novosibirsk have tested the remains of Stone Age people that had been found in southern Siberia, in the region of Gorny Altai. They have also tested samples from the corpses of men who had died during viral epidemics in the 19th Century and were buried in the Russian permafrost.
The researchers say they have found bodies with sores characteristic of the marks left by smallpox. While they did not find the smallpox virus itself, they have detected fragments of its DNA.
Certainly it is not the first time that bacteria frozen in ice have come back to life.
In a 2005 study, NASA scientists successfully revived bacteria that had been encased in a frozen pond in Alaska for 32,000 years. The microbes, called Carnobacterium pleistocenium, had been frozen since the Pleistocene period, when woolly mammoths still roamed the Earth. Once the ice melted, they began swimming around, seemingly unaffected.
Once they were revived, the viruses quickly became infectious.
Two years later, scientists managed to revive an 8-million-year-old bacterium that had been lying dormant in ice, beneath the surface of a glacier in the Beacon and Mullins valleys of Antarctica. In the same study, bacteria were also revived from ice that was over 100,000 years old.
We may be about to find out or maybe we already have. Climate change is melting permafrost soils that have been frozen for thousands of years, and as the soils melt they are releasing ancient viruses and bacteria that, having lain dormant, are springing back to life.
With the temperature rising all across the Arctic and Antarctica, the ice is melting faster than ever before.