Melting Permafrost Could Unleash Dormant Pathogens From the Past, Experts Warn

Climate change is causing the Earth's cryosphere, the frozen parts of the planet, to melt at an alarming rate.

This melting not only affects the sea level, the weather, and the ecosystems, but also poses a potential threat to human health.

The cryosphere, which includes glaciers, ice caps, snow, and permafrost, is home to a vast diversity of microorganisms, some of which are pathogens that can cause diseases in humans and animals.

These pathogens have been preserved in the ice for thousands or even millions of years, but as the ice melts, they may be released into the environment and pose a risk of infection or re-emergence.

Examples of 'time-traveling' pathogens in melting permafrost

(Photo : OLIVIER CHASSIGNOLE/AFP via Getty Images)

One of the most striking examples of "time-traveling" pathogens in melting permafrost is the case of an anthrax outbreak in Siberia in 2016, as per Phys.org.

Anthrax is a bacterial disease that can infect humans and animals, causing skin lesions, septicemia, and death.

Anthrax spores can survive in the soil for decades or even centuries and can be transmitted by contact with infected animals or contaminated products.

In 2016, a heat wave in Siberia caused the permafrost to thaw, exposing the carcasses of reindeer that had died from anthrax decades ago.

The anthrax spores became active and infected more than 2,000 reindeer and 96 people, killing one child. The outbreak prompted a massive vaccination campaign and a state of emergency in the region.

Another example of time-traveling pathogens in melting permafrost is the discovery of giant viruses that have been dormant for thousands of years.

Giant viruses are a group of viruses that are much larger than typical viruses and have complex genomes. Some of them can infect amoebas, which are single-celled organisms that live in water and soil.

In 2014, a team of scientists from France and Russia isolated two giant viruses from a 30,000-year-old permafrost sample from Siberia.

The viruses, named Pithovirus sibericum and Mollivirus sibericum, were still infectious and able to infect amoebas in the laboratory.

The scientists warned that more ancient viruses could be revived by the melting of permafrost and potentially infect humans or animals.

Also Read: Potential Pandemic Threat: A 'Relative' of the Deadliest Viruses in the World Successfully Isolated in Europe

Mechanisms of 'time-traveling' pathogens in melting permafrost

How can pathogens survive for such long periods of time in frozen environments? And how can they become active and infectious again after being released from their icy prison?

The answers to these questions depend on several factors, such as the type of pathogen, the freezing conditions, and the exposure to environmental changes, as per CNN.

Some pathogens, such as bacteria and spores, have mechanisms that allow them to enter a state of dormancy or low metabolic activity when faced with unfavorable conditions, such as freezing temperatures or lack of nutrients.

In this state, they can resist damage from ice crystals, dehydration, or oxidation.

When the conditions become favorable again, such as thawing temperatures or availability of hosts or nutrients, they can resume their normal activity and growth.

Other pathogens, such as viruses, do not have metabolic activity and rely on their host cells for replication.

Viruses can survive freezing by being protected by organic matter or ice matrices that prevent their degradation or inactivation.

When they encounter suitable host cells again, they can attach to them and inject their genetic material to initiate infection.

The risk of infection or re-emergence of 'time-traveling' pathogens in melting permafrost depends on several factors, such as the virulence and transmissibility of the pathogen, the susceptibility and immunity of the host population, and the environmental factors that influence the exposure and transmission pathways.

For example, some pathogens may require intermediate hosts or vectors to infect humans or animals, such as mosquitoes or ticks. Others may require direct contact or inhalation to cause infection.

The risk may also vary depending on the geographic location and socio-economic conditions of the affected regions.

For example, some regions may have limited access to healthcare services or surveillance systems that can detect and respond to outbreaks. Others may have high population density or mobility that can facilitate the spread of diseases.

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