‘Viral spillover risk’ means

Source: By The Indian Express

The effects of climate change range are being witnessed across a range of environments – from changes in crop yields due to unreliable weather conditions to the extinction of species. According to new research, yet another effect could be the increased risk of “viral spillover” in some regions that could cause new pandemics over the next few years.

Climate change could shift the species range of certain viral vectors and reservoirs northwards, and the High Arctic zone could become fertile ground for emerging pandemics.

This result was drawn from a research article titled, ‘Viral spillover risk increases with climate change in High Arctic lake sediments’, which was published on 19 October 2022 in Proceedings of the Royal Society B, the biological research journal of the UK’s The Royal Society.

What is viral spillover?

Viruses are some of the most abundant entities on earth, but they need to infect a host’s cell in order to replicate. According to the research, these virus/host relationships seem relatively stable within superkingdoms, the major groupings of organisms. However, below this rank, viruses may infect a new host from a reservoir host (in which it usually resides) by being able to transmit sustainably in a novel host – a process defined as ‘viral spillover’.

The Study

To study the possibility of a viral spillover, researchers from the University of Ottawa collected sediment and soil samples from Lake Hazen in Canada – the largest High Arctic lake by volume in the world, and the region’s largest freshwater ecosystem.

Then they undertook DNA and RNA sequencing to reconstruct the lake area’s virus composition. They estimated the spillover risk and found that the chances of a virus moving to a new host increases with runoff from glacier melt, treated by them as a proxy for climate change. As temperatures increase, the melting of glaciers increases as well, and there is a greater possibility for previously ice-trapped viruses and bacteria to find new hosts.

The Result

In this study, while it was found that the risk of viral spillovers increases with changes in the environment at a particular location, driven by global warming, this by itself does not guarantee a higher possibility of a pandemic occurring via viruses here. “Altogether, we provided here a novel approach to assessing spillover risk…This is not the same as predicting spillovers or even pandemics,” said the authors.

This is because there is another important link in the process. As long as viruses and their ‘bridge vectors’ – that act as hosts and lead to their spread – are not simultaneously present in the environment, the likelihood of dramatic events probably remains low. However, that does not by itself signal relief. The authors said, “Climate change leads to shifts in species ranges and distributions, new associations can emerge, bringing in vectors that can mediate viral spillovers, as simulations recently highlight.”