PITTSBURGH, Oct. 5 (UPI) -- Biologists at the University of Pittsburgh say they've found thousands of undiscovered viruses in sewage, some of which could relate to human health.

The approximately 1.8 million species of organisms on Earth each host untold numbers of unique viruses yet only about 3,000 have been identified to date, a university release said Wednesday.


To begin to characterize these unknown viruses, Pittsburgh biologists are developing new techniques to look for novel viruses in unique places around the world.

The researchers said raw sewage proved to be home to the most diverse array of viruses ever found.

"What was surprising was that the vast majority of viruses we found were viruses that had not been detected or described before," Pittsburgh researcher Roger Hendrix said.

New computational tools will allow researchers to analyze the data in an approach called metagenomics.

"The big question we're interested in is, 'Where do emerging viruses come from?'" Hendrix said.

The researchers said they believe new viruses emerge, in large part, through gene exchange, but large number of viruses must be studied to test this theory.

"First you have to see the forest before you can pick out a particular tree to work on," researcher James Pipas said. "If gene exchange is occurring among viruses, then we want to know where those genes are coming from, and if we only know about a small percentage of the viruses that exist, then we're missing most of the forest."