Scientists at San Diego State University have stumbled upon a widespread gut virus that was previously unknown, which could play a key role in the onset of diabetes and obesity.

Over half of the world’s population has this newly detected gut virus, called crAssphage, which infects Bacteroidetes, a highly common gut bacteria. The phylum Bacteroidetes is widely prevalent in the environment, and exists in sea water, soil, sediments, and in the guts of animals and humans.

The SDSU biologists happened to discover the gut virus while examining the DNA fecal samples of 12 individuals. They noticed a specific cluster of viral DNA that all the samples contained. However, the virus they discovered did not match anything related to any known viruses.

They proved the existence of the viral DNA in nature using a technique known as DNA amplification, which located the virus in the original samples to develop the National Institute of Health’s (NIH) database.

Robert A. Edwards, a bioinformatics professor at SDSU, and his colleagues are shocked at how long the virus has gone undetected, considering how widespread it appears to be.

“It’s not unusual to go looking for a novel virus and find one,” Edwards said. “But it’s very unusual to find one that so many people have in common. The fact that it’s flown under the radar for so long is very strange,” said Edwards in a statement.

The scientists have found the virus in all populations examined, and concluded that it’s essentially as old as the human race.

The new research appears in the journal Nature Communications.