"They've been sitting there for at least 19 million years, far longer than anyone previously thought this family of viruses had been in existence," said Cédric Feschotte and Clément Gilbert, associate professor and member of the UT Arlington Genome Biology Group and post-doctoral research associate in the group, respectively.
"Whereas we previously thought of hepadnavirus evolution on time-scales of only a few thousand years, this paper shows that the true time-scale is in fact many million years. Therefore, hepadnavirues, and likely many other viruses as well, are far older than we previously thought," said Eddie Holmes, a distinguished professor of biology at Penn State University.
Feschotte believes that the slow evolution of the viruses in birds indicates that the viruses are, in the long run, better adapted to their hosts than what is suggested by study of the disease-causing Hepatitis B viruses.
The study could be important for research that might help predict and prevent human viral pandemics originating in bird species.
"We can therefore use this discovery as a guide to screen targeted groups of bird species for the presence of new circulating Hepatitis B-like viruses," said Gilbert.
The article will be published next week in the online, open access journal PloS.