TOKYO (AFP) – A warming climate could bring viruses in the Arctic into contact with new environments and hosts, increasing the risk of “viral spillover”, according to research published on Wednesday.
Viruses need hosts like humans, animals, plants or fungi to replicate and spread, and occasionally they can jump to a new one that lacks immunity, as seen during the COVID-19 pandemic.
Scientists in Canada wanted to investigate how climate change might affect spillover risk by examining samples from the Arctic landscape of Lake Hazen. It is the the largest lake in the world, in the north of the Arctic Circle, and “was truly unlike any other place I’ve been”, researcher and medical student, at the University of Toronto, Graham Colby told AFP.
The team sampled soil that becomes a riverbed for melted glacier water in the summer, as well as the lakebed itself – which required clearing snow and drilling through two metres of ice, even in May when the research was carried out. They used ropes and a snowmobile to lift the lake sediment through almost 300 metres of water, and samples were then sequenced for DNA and RNA, the genetic blueprints and messengers of life.
“This enabled us to know what viruses are in a given environment, and what potential hosts are also present,” said an associate professor in the University of Ottawa’s biology department, Stephane Aris-Brosou. But to find out how likely they were to jump hosts, the team needed to examine the equivalent of each virus and the host’s family tree.
“Basically what we tried to do is measure how similar these trees are,” said the first author of the research, Audree Lemieux.
Similar genealogies suggest a virus has evolved along with its host, but differences suggest spillover.
And if a virus has jumped hosts once, it is more likely to do so again.The analysis found pronounced differences between viruses and hosts in the lakebed, “which is directly correlated to the risk of spillover”, said Aris-Brosou.
The difference was less stark in the riverbeds, which the researchers theorise is because water erodes the topsoil, removing organisms and limiting interactions between viruses and potential new hosts.
Those instead wash into the lake, which has seen ‘dramatic change’ in recent years, the study said, as increased water from melting glaciers deposits more sediment.
“That’s going to bring together hosts and viruses that would not normally encounter each other,” Lemieux said.
The research authors, published in the Proceedings of the Royal Society B: Biological Sciences journal, caution they are neither forecasting an actual spillover nor a pandemic.
“The likelihood of dramatic events remains very low,” Lemieux said.
They also warn more work is needed to clarify how big the difference between viruses and hosts needs to be to create serious spillover risk. But they argued that warming weather could increase risks further if new potential hosts move into previously inhospitable regions.