Influenza viruses may have originated in fish 600 million years ago

A flu virus found in a sturgeon hints that influenza viruses originated in fish around 600 million years ago and evolved with their hosts to infect a wide range of species today.

Influenza viruses cause illness in many vertebrates, including humans, birds, cats, whales and dolphins, but little is known about how they first evolved.

In 2018, researchers identified a virus from a hagfish that resembled a predicted ancestral form of …