The flu virus may have started at sea, as discovered by researchers analyzing genetic databases. Scientists believe that the influenza family of viruses likely originated. in primitive aquatic animals that evolved hundreds of millions of years ago, long before the first fish.
The viruses in this group seem particularly adept at jumping from one host to another, says Mary Petrone, a virologist at the University of Sydney in Australia and co-author of the study. And knowing what those jumps are could help scientists identify viruses that have the potential to trigger new outbreaks among humans.
History of the origins of the flu
Like many virologists, Petrone spent the first two years of the epidemic intensively studying SARS-CoV-2. But when he moved to Australia to do postdoctoral research, Petrone wanted to spend time in one of the country’s most famous ecosystems. “After working on Covid for two years, I thought going to the coral reefs to do fieldwork sounded really good,” she says.
Corals are part of a phylum called cnidariadescended from other animals about 600 million years ago. Petrone hoped that studying corals could reveal the deeper history of viruses that infect animals, particularly those with RNA genomes. This viral group includes numerous human and animal pathogens.
Petrone’s first call was not to a dive shop, but to Zoe Richards, a coral researcher at Curtin University in Bentley, Australia, who provided samples of two coral species collected off the coast of Western Australia. Analysis of RNA collected in corals provided evidence of virus infection. belonging to a group called articulaviralincludes the influenza virus family and a group called quarantine virus. Members of the second group roam in ticks and occasionally sneak into humans, birds, and other vertebrates.
The new research suggests that the viruses that infect corals are part of an ancient viral family that likely arose around 600 million years ago.and later caused other members to appear articulaviralincluding the flu and quarantine virus.
Hagfish Secrets
Discovery Petrone wondered if flu viruses were also born at sea.. In fact, there was already some evidence of that. In 2018, researchers identified a distant relative of the flu in a porpoise. These slimy, jawless creatures descend from an early vertebrate lineage, and the study’s authors suggest that the flu co-evolved with vertebrates.
Consulting genetic databases, Petrone Flu-related RNA sequences found in Siberian sturgeon samples (Acipenser Baerii). Sturgeons are jawed vertebrates that are closer to humans than hagfish. But the sturgeon virus branched out from the main flu family tree before all other known flu viruses, including the hagfish virus.
Discovery of the first two strains of influenza flu likely infected aquatic animals, including fish, before it landedsays Petrone. But it’s unclear whether the flu first moved to land via terrestrial vertebrates or whether it spread from sea to land more recently.
To determine this, the researchers say they need to look for flu relatives in more animals and better understand how the virus spreads between host species.
born at sea
Jie Cui, an evolutionary virologist at Shanghai’s Pasteur Institute in China, agrees that the flu and its wider family likely originated in the sea. In 2021, his team analyzed deep-sea lobster genomes and identified viruses that were part of the larger group 3 flu. “There’s a lot of untapped viral diversity in aquatic environments,” he says.
Robert Gifford, an evolutionary virologist at the University of Glasgow, England, says: It would be surprising to find a significant group of viruses that do not occur in aquatic environments due to the ancient nature of marine life. “The study provides convincing evidence that influenza viruses are of aquatic origin.”
Identifying legacy hops between hosts is also can help researchers assess the risk to humans that certain viruses posetell the authors. Petrone’s team found signs that tick-infected quaranjaviruses may have spread to the creatures after first circulating in crustaceans.
The discovery of such jumps is the result of studies on water viruses “can help us better understand the historical emergence and evolution of viruses zoonotic potential,” adds Chantal Vogels, an arbovirologist at the Yale School of Public Health in New Haven, Connecticut.
Gifford acknowledges that studies like Petrone’s can help identify viruses that have the ability to cause epidemics in humans and other animals. But he warns that conclusions about former host jumps may change as the viral family tree becomes more populated and relationships rearrange.
Reference work: https://www.biorxiv.org/content/10.1101/2023.02.15.528772v1
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