April 4 (UPI) -- Most modern viruses have ancient roots. New research suggests RNA viruses are millions of years old, many tracing their evolutionary histories back to the earliest vertebrates. Some viruses may be as old as the first animals.
In an effort to find new RNA viruses, a team of researchers from Australia and China examined 186 vertebrate species most ignored as potential viral hosts. Their search yielded 14 novel RNA viruses -- viruses with RNA, or ribonucleic acid, as its genetic material.
Scientists located the viruses in seemingly healthy amphibians, reptiles, lungfish, ray-finned fish, cartilaginous fish and jawless fish.
The research, detailed in the journal Nature, puts the evolutionary origin of RNA viruses -- a family that includes human pathogens such as influenza virus -- as far back as the emergence of the first vertebrates.
Previous studies have shown that most viruses can trace their lineage as far back as the evolutionary origins of the vertebrates in which they're found.
"This study reveals some groups of virus have been in existence for the entire evolutionary history of the vertebrates -- it transforms our understanding of virus evolution," Eddie Holmes, a researcher at the University of Sydney, said in a news release. "For the first time we can definitely show that RNA viruses are many millions of years old, and have been in existence since the first vertebrates existed."
The study revealed a remarkable diversity of viruses among fish species, including relatives of Ebola and influenza.
The newly discovered viruses are not a threat to human health, according to Holmes and his colleagues. Viral diversity is a natural part of evolution.
"This study emphasizes just how big the universe of viruses -- the virosphere -- really is. Viruses are everywhere," Holmes said. "It is clear that there are still many millions more viruses still to be discovered."