Global warming: Africa, Asia most at risk of zoonotic spillovers

There can be 15,000 instances of viruses jumping from one species to another over the next 50 years

By DTE Staff
Published: Monday 02 May 2022

Climate and land-use change would open opportunities for virus sharing among previously geographically isolated species, according to a new report.

The host species contributing to the spillover will be concentrated in certain geographies, the study published in the journal Nature April 28, 2022 showed. These include high elevations, in biodiversity hotspots and in areas of high human population density in Asia and Africa, driving the cross-species transmission of novel viruses at least 4,000 times.

A majority of the 10,000 virus species that have the capacity to infect humans are moving silently in the wild mammals at present, the report noted.

Exchange of pathogens among species is still not very common: Of all possible pairs of mammal species, only 7 per cent share any geographic range, and only 6 per cent are currently known to host one or more of the same virus species / viral sharing. 

As host geographic ranges shift, some interactions will become possible for the first time, and a subset will lead to viral establishment in a previously-inaccessible host (novel viral sharing), according to Climate change increases cross-species viral transmission risk.

At the global level, geographic range shifts would permit over 300,000 first encounters in every scenario of global warming. The Intergovernmental Panel on Climate Change designed four scenarios to project how concentrations of greenhouse gases in the atmosphere will change with time and what repercussions each scenario can have.

The first scenario, Representative Concentration Pathway (RCP) 2.6, would lead to 316,426 novel species interaction and RCP 8.5, the final scenario, to 313,973 encounters.

The report added:

A total of 316,426 first encounters in RCP 2.6 will lead to 15,311 novel sharing events, a minimum of at least 15,000 cross-species transmission events of at least one novel virus (but potentially many more) between a pair of naive host species.

In other words, there can be 15,000 instances of viruses jumping from one species to another over the next 50 years, the researchers wrote. Climate change can thus fuel further pandemics like COVID-19, they added. 

Potential hotspots of future viral sharing were simulated, using a phylogeographic model of the mammal-virus network, and projections of geographic range shifts for 3,139 mammal species under climate change and land-use scenarios for the year 2070.

Bats with their dispersal capacity account for a majority of novel viral sharing and are likely to share viruses along evolutionary pathways that can facilitate future emergence in humans, the report said.

This ecological transition may already be underway, the authors warned. Restricting global warming to 2 degrees Celsius over pre-industrial levels within the century may not reduce new viral sharing, due to greater potential range expansions, they added.

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