Mammals harbour at least 320,000 new viruses

There are a minimum of 320,000 new viruses in mammals yet to be discovered, and identifying them could prove key to early detection and mitigation of disease outbreaks in humans, scientists say.
Close to 70 per cent of emerging viral diseases such as HIV/AIDS, West Nile, Ebola, SARS, and influenza, are zoonoses - infections of animals that cross into humans.
Yet until now, there has been no good estimate of the actual number of viruses that exist in any wildlife species.
"Finally we have a breakthrough - there aren't millions of unknown virus, just a few hundred thousand, and given the technology we have it's possible that in my lifetime, we'll know the identity of every unknown virus on the planet," said Peter Daszak, corresponding author and president of EcoHealth Alliance.

To address the challenges of describing and estimating virodiversity, a team of investigators from Center for Infection and Immunity (CII) and EcoHealth Alliance began in jungles of Bangladesh - home to the flying fox.
These bats are the largest flying mammal with a wingspan of up to 6 feet, they are also the source of several outbreaks of Nipah virus. The team collected 1,897 biological samples from the animals, which were captured and released.

In the lab, they used polymerase chain reaction to identify 55 viruses in nine viral families. Of these, only five were previously known, including two human bocaviruses, an avian adenovirus, a human/bovine betacoronavirus, and an avian gammacoronavirus.

Another 50 were newly discovered, including 10 in the same family as Nipah. Next the researchers adapted a statistical technique from the field of ecology to estimate that there were another three rare viruses unaccounted for in the samples, upping the estimate of viruses in the flying fox to 58.
Finally, this number was extrapolated to all 5,486 known mammals, yielding a total of at least 320,000 viruses.
The researchers say the initial estimate of 320,000 is just a starting point and will likely be considerably higher after accounting for additional viral families and employing high throughput sequencing methods developed at CII.