A team of researchers has discovered more than 200 viruses in fish, frogs and other reptiles, some of which carry diseases such as influenza and haemorrhagic fevers. The researchers also traced the origin of these RNA viruses, which have been dated to hundreds of millions of years ago, when most modern animals began to appear.
A team of researchers led by Mya Breitbart, a virologist at the University of South Florida in Tampa, highlights their discovery RNA viruses and their evolution over the years. The study of theses viruses can help predict how these viruses can infect humans in the future. Until now, researchers have been looking at viruses that infect humans, mammals and birds. This is the first time they have turned to other vertebrates such as amphibians, reptiles and fish to understand how these viruses have evolved over the millennia.
Edward Holmes, an evolutionary virologist at the University of Sydney in Australia – and co-author of the study – notes that the emergence of viruses is actually much more abundant and widespread than previously thought. Previous studies have found RNA viruses in both newts and salamanders. But the researchers here looked at nearly 190 other creatures, jawless fish like lampreys for example, which have evolved little compared to their evolutionary ancestors, to reptiles such as turtles. By analyzing the RNA extracted from the intestines, liver, lungs or gills of the animals, the team discovered 214 RNA viruses that had never been recorded before.
Most of these viruses belong to families of viruses known to infect birds and mammals. For example, some fish harbor viruses that are linked to Ebola, which affects humans and other primates. “It’s surprising,” says Holmes, but that does not mean that these viruses pose a threat to human health.
Going up the evolutionary tree of these new RNA viruses, and comparing them to that of their vertebrate hosts, the two stories match: vertebrates migrated from the sea to the earth, just like their microscopic hitchhikers .
The RNA viruses that infect humans today have probably evolved from viruses that infected our vertebrate ancestors 500 million years ago, the researchers note. The discovery of these viruses will help scientists and doctors in the precise diagnosis and treatment of diseases caused by viruses. Recall that many serious human diseases such as AIDS, Ebola, SARS and influenza are caused by RNA viruses.