Feral Fire Under the Ice

The apocalyptic consequences stemming from climate change have been well-documented. Most recently, the Siberian Arctic region witnessed a record-breaking heatwave, fuelling fresh concerns about the melting of the Earth’s cryosphere. If global warming continues at this rate, it is estimated that there will be a 60 per cent thaw in permafrost by 2100. Covering more than 20 per cent of the Northern Hemisphere, the melting of the permafrost can be catastrophic since it has the potential to release enormous reserves of greenhouse gases and destroy the infrastructure it supports.

From a biosecurity perspective, however, there is a far bigger threat. As the planet warms and the ice thaws, the Earth’s ancient and forgotten pathogens, which have been trapped or preserved for thousands of years, may re-emerge with new vigour. On coming into contact with the right host, they can unleash a series of diseases that have remained dormant for a long time.

SKULKING MICROBES

Permafrost is the frozen subsurface layer of soil that remains below 0°C for two or more consecutive years. It is an ideal abiotic reservoir for glacial microbes and viruses, as it is cold, dark, and anoxic. With an increase in global temperatures, the topmost layer of this permafrost, which thaws every summer, has been growing deeper. This is enough to activate biological processes that awaken the frozen microbes and facilitate their movement towards the ‘talik’, a layer of unfrozen ground lying above the permafrost.

Some of these pathogens are already familiar to the scientific community. For instance, in Siberia, a recent outbreak of Anthrax among reindeer herds and humans was attributed to the Bacillus anthracis, a pathogen well-known to mankind. There could, however, be other permafrost-locked microbes with unknown infectivity, lurking in the dark recesses of permafrost soils. The 28 new virus groups that were recently discovered from ice core samples in the northwestern Tibetan Plateau of China is a case in point.

TRANSMISSION PATHWAYS

Once freed from their frozen states, permafrost microbes need a human or animal host to perpetuate. This can prove to be challenging in the Arctic region since it is sparsely inhabited. Even if the pathogens manage to infect indigenous populations, the risk of large-scale transmission is low, owing to their minimal contact with the outside world.

In recent years, however, this status quo has been rapidly changing. With the melting of the Arctic sea ice, the northern shore of Siberia has become more accessible by sea. Therefore, corporations and governments are looking to explore new shipping routes and expand the land available for drilling or mining in the region. This pursuit of oil, gas, rare earth and other minerals has increased human exposure to viable virions in the Polar region.

Similarly, animals have also been traversing new passageways and spreading disease. A paper published by the researchers at One Health Institute analyses how melting sea ice may facilitate the spread of a disease called Phocine Distemper Virus (PDV) among marine mammals. In light of this evolving reality, the possibility of pathogens being transmitted through environmental pathways like thawed ice or melted water can no longer be ignored.

THREAT OF VIRUS VECTORS

Among the various pathogenic microbes preserved in the permafrost, it is the viruses that are a major cause for concern. Many of them are believed to have triggered global pandemics in the past. For instance, scientists have discovered fragments of RNA from the 1918 Spanish flu virus, in corpses that have been buried in mass graves at the Alaskan tundra.

As opposed to RNA viruses, DNA viruses are hardier and more chemically stable, which means that they can emerge from their frozen state relatively intact. Consequently, they are considered to be a far bigger threat by certain experts. In the 1990s, for example, scientists from the State Research Center of Virology and Biotechnology in Novosibirsk, detected fragments of smallpox DNA on the remains of people whose bodies had been mummified in Southern Siberia since the Stone Age.

Similarly, a 2014 study was able to revive two viruses, Pithovirus sibericum and Mollivirus sibericum, which had been trapped in the Siberian permafrost for over 30,000 years. Fortunately, their resurrection did not constitute a global health risk, as the viruses only attacked single-celled amoebas with the ability to shift shapes. Nonetheless, such discoveries sound the alarm for deadlier viruses that lie in wait within the active layers of permafrost.

In so far as bacterial vectors are concerned, frozen ice is an ideal place for them to thrive over long periods of time. In 2005, NASA scientists were able to successfully revive bacteria that had been encased in a frozen pond in Alaska since the Pleistocene period. More than ten years later, the thawing of permafrost in the Yamal Peninsula exposed the frozen carcass of a reindeer that was infected with Anthrax. With the melting of permafrost, this infectious Anthrax had been released into the nearby water and soil, gradually entering the food chain and infecting reindeers that had grazed there. In the latest discovery yet, a team of evolutionary geneticists have extracted DNA samples from the remains of 40 human skeletons in Eastern Siberia, two of which contain traces of the bacterium that causes plague.

Not all bacteria, however, can come back to life after being frozen in permafrost. Many do so because they form spores that are extremely hardy. This includes Anthrax, Tetanus and Botulism. Even more ominously, some of the discovered bacteria have demonstrated antibiotic resistance. In fact, multiple antibiotic-resistant bacteria have been recovered from the Siachen glacier in the Himalayas. By acting as reservoirs of pathogenic drug-resistant bacteria, such frozen zones can encumber global measures to contain antimicrobial resistance.

Finally, global warming has enabled fungal communities preserved in ice to adapt to higher temperatures, thereby helping them to overcome geographical thermal barriers. Some of these, like Cryptococcus, are notorious pathogens for the immuno-compromised. Others like Candida auris also display multidrug resistance.

Bearing all these risks in mind, a global framework for pandemic prevention, which facilitates collaboration between environmental scientists and health professionals must be formulated. It is important to address anthropogenic causes of climate change that increase the possibility of disease transmission.

Assessment

• The interoperability of technical data will be crucial in mitigating the risks posed by ice-based transmission pathways. Weather tracking satellites can help to forecast diseases based on atmospheric, land and weather data. Establishing microbial listening posts for surveillance and harvesting the data from such hotspots can also facilitate institutional monitoring. Towards this end, a cloud-based cyber infrastructure must be created to process relevant inputs.
• The broader imperative is to turn the clock back on humankind’s unsustainable ways of living. It is important to peaceably co-exist with other life forms and reduce the anthropogenic footprint on shared environments.
• In this regard, countries must strengthen the link between their health and climate agendas. The global community must invest more heavily in sectors that help to cap global warming at under 2°C.