Where do viruses like the flu come from?

We all know, or should know, that, based on the available evidence, life on Earth began in water, and was for a long time confined to the sea.

But viruses? Where did parasites like those that cause the flu originate?

In a new work, analysis of RNA collected from corals has demonstrated the infection of polyps by viruses that belong to a group called Articulavirales, which includes the family of flu virus and a group called Quaranjaviruses. Members of the latter group circulate in ticks and occasionally flock to humans, birds, and other vertebrates.

New analysis suggests viruses that infect corals are part of an ancient viral family that probably emerged about 600 million years ago and which later gave rise to the other members of the Articulavirales, including the influenza viruses.

That this was the case, it was previously assumed: in 2018, researchers identified a distant relative of influenza in lampreys. These jawless creatures are among the most primitive living vertebrates, suggesting that the flu virus may have co-evolved with vertebrates.

Even more primitive viruses of the Articulovirales group, which split from the branch that led to influenza even earlier than those that infect lampreys today, have also been found in Siberian sturgeons, in which viral RNAs of previously unknown parasites have been isolated .

Furthermore, the aquatic evolution of influenza viruses has not only produced vertebrate parasites: in 2021, analyzing samples of deep-sea lobsters, viruses were identified that are part of the group that also includes influenza.

One could naturally think that it is obvious that, given the evolution of animals starting from the sea, the viruses that infect them are also present in this environment, and since ancient times; however, there are less obvious questions that arise from this observation. For example, how recently did the infection of terrestrial species occur? Before or after the conquest of the mainland by vertebrates? In modern or very ancient times? To date, it is not yet possible to establish this, because data from many more different bodies is needed than is available today.

However, answers to questions such as the previous ones are not without consequences.

In fact, if it were to turn out that in modern times there is still a sustained flow of virosis from the sea to the mainland, our very concept of zoonosis, and therefore of a source of evolutionary variety that can lead to subsequent pandemic adaptations, would have to be profoundly revised.

If the species acting as a reservoir for the progenitors of pandemic viruses are also to be extended to marine ones, the variety and possibility of health problems changes in scale: both for the diversity of marine life and for the circulation of the organisms that compose it , and finally for the different forms of contact between human beings and that type of fauna.

It is for this reason that the type of research illustrated is interesting and useful not only for evolutionary biologists, but also for the prevention and quantification of global health risks, strictly from a “One-Health” perspective.

Perhaps, after all, not only Venus has emerged from the sea foam, but also some annoying or dangerous housemates of this planet, and to settle this point will not be without consequences.