Thawed ancient pathogens might unleash global chaos

Thawed ancient pathogens may pose severe ecological risks, and adequate preparation is key to averting disaster.
John Loeffler
Pithovirus sibericum
Pithovirus sibericum

Jean-Michel Claverie/IGS/CNRS-AM 

New research shows how dramatic the release of ancient pathogens from thawing ice and permafrost can be for Earth’s ecosystem, even under extremely conservative modeling.

The revival of long-frozen bacteria isn’t some far-fetched idea either. Specimens procured from an ice core that had been bored into an ice cap on the Qinghai-Tibetan plateau in 2003 were more than 750,000 years old and were successfully reanimated.

In 2014, a giant Pithovirus sibericum, one of the more recent so-called zombie viruses, was resurrected from Siberian permafrost that had been frozen for 30,000 years.

A 2016 anthrax outbreak in western Siberia, leading to the death of thousands of reindeer and affecting many people, was traced back to thawing spores of Bacillus anthracis, the bacterium responsible for anthrax, within the Siberian permafrost.

Additionally, recent research highlighted significant genetic compatibility between viruses discovered in Arctic lake sediments and possible living hosts.

An unfathomably large number of ancient microorganisms might be released every year

The Earth's climate is warming at an alarming speed, with the cold Arctic regions witnessing up to four times the average warming speed. Forecasts predict the release of four sextillion microorganisms annually due to ice melt.

Nevertheless, despite the staggering number of microorganisms—including potential pathogens—being set free from melting ice, the actual risk they present to modern ecosystems remains unknown. A novel study published in the journal PLOS Computational Biology seeks to quantify the ecological dangers associated with the unforeseen release of ancient viruses.

“Our simulations show that 1% of simulated releases of just one dormant pathogen could cause major environmental damage and the widespread loss of host organisms around the world,” study co-author Corey J. A. Bradshaw and Giovanni Strona write in The Conversation this week.

Using Avida software, which helps to model biological environments for research purposes, the experiments the researchers ran mimicked the introduction of an ancient pathogen into modern biological communities. The impacts of this invading pathogen on the diversity of current host bacteria were measured in numerous simulations, and comparisons were drawn to simulations without pathogen invasion.

Invading pathogens stand an outside chance of dominating modern environments

Interestingly, the invading pathogens often managed to survive and adapt in the simulated modern world. In about 3% of the simulations, the pathogen emerged dominant in the new environment, subsequently leading to significant losses in modern host diversity. In the most drastic scenarios, the invasion led to a 30% reduction in the host community's size compared to control groups.

“The risk from this small fraction of pathogens might seem small, but keep in mind these are the results of releasing just one particular pathogen in simulated environments,” Bradshaw and Strona write. “With the sheer number of ancient microbes being released in the real world, such outbreaks represent a substantial danger.”

The findings point to the possibility that the dangers could become major catalysts for ecological change. Although the study did not consider potential human risks, the prospect of "time-travelling" pathogens establishing themselves and severely impacting host communities is unsettling enough.