Time-travelling ‘zombie’ viruses are reawakening from melting ice

Climate change could hasten the release of ‘time-travelling’ pathogens from melting permafrost and ice that have been trapped for millennia. Their emergence increases threats to the global environment and even humanity itself.

While melting glaciers and permafrost risk the re-emergence of many types of dormant pathogens, the potential destruction to modern ecosystems posed by these microbes has been difficult to predict.

A new study published in the journal PLOS Computational Biology has calculated the ecological risks posed by the release of these unpredictable ancient microbes.

The study, led by Dr Giovanni Strona of the European Commission Joint Research Centre and Professor Corey Bradshaw of Flinders University in Australia, used computer simulations to model the impact of ancient pathogens on bacterial communities.

The researchers constructed simulated experiments where digital pathogens from the past invade communities of bacteria-like hosts. They compared the effects of the invading pathogens on the diversity of host bacteria to those in communities where no invasions occurred.

They found that in their simulations, the ancient invading pathogens could often survive and evolve in the modern world, and about 3% became dominant in their new environment.

The risks posed by this 1% of released pathogens might seem small, but given the sheer number of ancient microbes regularly released into modern communities, the researchers say these outbreaks represent a substantial danger.

‘The scientific debate on the topic has been dominated by speculation, due to the challenges in collecting data or designing experiments to elaborate and test hypotheses. For the first time, we provide an extensive analysis of the risk posed to modern ecological communities by these “time-travelling” pathogens through advanced computer simulations,’ said lead author Dr Giovanni Strona.

‘We found that invading pathogens could often survive, evolve and, in a few cases, become exceptionally persistent and dominant in the community, causing either substantial losses or changes in the number of living species. Our findings therefore suggest that unpredictable threats so far confined to science fiction could in reality pose serious risk as powerful drivers of ecological damage.’

The researchers used Avida, an artificial-life software platform developed by Michigan State University, to construct and test the simulated release of the digital pathogens into biological communities.

Professor Corey Bradshaw said the new findings show that the risk of invasion of unknown ‘black swan’ pathogens that can cause irreversible damage is not negligible.

‘From that perspective, our results are worrisome, because they point to an actual risk deriving from the rare events where pathogens currently trapped in the permafrost and ice produce severe ecological impacts. In the worst, but still entirely plausible case, the invasion of a single ancient pathogen reduced the size of its host community by 30% when compared to our non-invasive controls.’

‘As a society, we need to understand the potential risk posed by these ancient microbes so we can prepare for any unintended consequences of their release into the modern world. The results tell us that the risk is no longer simply a fantasy that we shouldn’t be prepared to defend against.’

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