'Good' Viruses Can Protect Your Gut

You've likely heard of "good" bacteria in the human gut - the little guys that live in balanced communities and constantly keep one another in check, as well as keep invaders out. However, could the same hold true for viruses? In a new study, researchers investigate this question.

The study, recently published in the journal Nature, describes how researchers set out to see if harmless virus populations could help bolster a body's natural defense against invaders, much like a diverse microbiome does in the gut.

To determine this, a team from the New York University School of Medicine and the New York Presbyterian Hospital gave several groups of healthy mice the rodent equivalent of norovirus - the same virus that commonly makes headlines for ruining cruise trips with rampant food poisoning.

In healthy mice, norovirus can persist without causing any outward symptoms. This made it an excellent candidate for determining if unnoticed viral lodgers can help protect a host from dangerous infection.

The norovirus mice and an unexposed group were then given antibiotics that wiped out the majority of their gut flora. As seen among patients enduring extended hospital stays, this left them wide open for attack by new bacteria.

The team then infected these mice groups with a bacterial pathogen similar to E. coli. Stunningly, the mice "pre-treated" with the norovirus showed far fewer signs of bacterial infection and suffered from only mild symptoms, compared to the mice that had not been exposed to the norovirus.

This could indicate that viruses dwelling unnoticed in any animal, humans included, could potentially interfere with harmful infections. Lead author Ken Cadwell even told New Scientist that viruses are routinely detected in young children who don't show any symptoms, and also in people recovering from acute bacterial infections of the gut.

This could mean that their presence is helpful to the human body during times of vulnerability.

However, he adds that it's hard to tell which viruses will have an adverse effect on humans. The norovirus, for example, is certainly not a good option for people.

"Perhaps we can have the good without the bad," he said, suggesting that researchers look into replicating the "good" actions of viruses without using them directly.