(ORDO NEWS) — Biologists have discovered influenza RNA in sturgeons.
Its genome is surprisingly close to what the ancestors of today’s influenza viruses might have had. Perhaps it was from fish that other animals once began to become infected with this infection.
The flu affects a huge variety of animals, from dolphins to humans, so it is still not clear exactly where and when these viruses originated.
In 2018, Chinese scientists found flu in hagfish, primitive jawless fish, and its RNA sequence was close to the genome of the alleged ancient ancestor of such viruses.
This suggested that the flu appeared in fish and only then began to adapt and infect other animals. This hypothesis is confirmed by the new work of biologists from the University of Sydney.
Influenza viruses belong to the broader RNA-containing Articulavirales phylum.
Mary Petrone and her co-authors analyzed the available sequencing data for “total RNA” – the entire array of these molecules that are synthesized by the cell – of different animal species and found that such viruses are found even in cnidarians (jellyfish and corals).
Scientists have named them Cnidenoviridae . According to biologists, it is these viruses that could be the basal group from which the entire variety of Articulavirales originates .
In addition, Mary Petron and colleagues used genetic databases to look for influenza in fish.
The primary target was a protein that plays a key role in viral RNA replication, and the corresponding gene was found in “total RNA” sequencing data from the intestines of sturgeons caught at an aquaculture farm in China.
Its sequence is 25 percent identical to that found previously in hagfish. Moreover, it turned out to be even more similar to the hypothetical ancient ancestor of influenza viruses.
Of course, the viruses that infect fish today cannot be called the same “common ancestors of influenza.”
However, it seems that it was fish that could have been their first hosts, and the prehistory of modern influenza began at least 600 million years ago, with cnidating marine invertebrates.
“The work provides compelling evidence that influenza viruses are of aquatic origin,” said microbiologist Robert Gifford of the University of Glasgow.
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