A newly discovered virus is harboring inside the guts of more than half the world's population, and has gone undetected by scientists or decades, according to a new study. (Photo : Flickr: James Palinsad)

A newly discovered virus is harboring inside the guts of more than half the world's population, and has gone undetected by scientists or decades, according to a new study.

The crAssphage virus infects one of the most common types of gut bacteria, Bacteroidetes, and is reportedly connected with obesity, diabetes and other gut-related diseases.

Lead study author Robert A. Edwards, a bioinformatics professor at San Diego State University (SDSU), and his colleagues stumbled upon this virus by accident.

In the DNA fecal samples from 12 different individuals, they noticed a particular cluster of viral DNA - about 97,000 base pairs long - present in all the samples.

Since the virus was unknown and not found in the National Institute of Health's Human Microbiome Project (HMP) database and Argonne National Laboratory's MG-RAST database, they used a DNA amplification technique to make the discovery.

"It's not unusual to go looking for a novel virus and find one," Edwards said in a statement. "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."

Since half of the sampled people were infected with this gut virus, researchers suspect that it's once that has been around for some time.

"We've basically found it in every population we've looked at," Edwards added. "As far as we can tell, it's as old as humans are."

Since some of the proteins in crAssphage's DNA are similar to those found in other well-described viruses, the SDSU team determined that it is a bacteriophage - meaning it infects and replicates inside bacteria.

Bacteriodetes bacteria live toward the end of the intestinal tract, and they are suspected to play a major role in the link between gut bacteria and obesity. In order to determine what role crAssphage plays in this process researchers will have to isolate the virus in future research.

"We know it's there, but we can't capture it quite yet," Edwards said.

The study's findings were published in the journal Nature Communications on July 24.