Norovirus and other ‘stomach viruses’ can spread through saliva, research finds

Scientists have shown that a group of viruses that are known to cause severe diarrheal illnesses, including the one infamous for massive outbreaks on cruise ships, may develop in mice’s salivary glands and spread through their saliva. The results demonstrate that these widespread viruses, which can be fatal and affect billions of people annually around the world, have a novel pathway of transmission.

The fact that these so-called enteric viruses are shared by saliva means that other methods of transmission, such as coughing, talking, sneezing, sharing food and utensils, and even kissing, may also be effective. Studies on humans are still required to corroborate the new findings. The results, which are published in the journal Nature, might result in more effective strategies to prevent, identify, and cure illnesses brought on by these viruses.

The study was led by the National Heart, Lung, and Blood Institute (NHLBI), part of NIH.

Researchers have known for some time that enteric viruses, such as noroviruses and rotaviruses, can spread by eating food or drinking liquids contaminated with fecal matter containing these viruses. Enteric viruses were thought to bypass the salivary gland and target the intestines, exiting later through feces. Although some scientists have suspected there may be another route of transmission, this theory remained largely untested until now.

Now researchers will need to confirm that salivary transmission of enteric viruses is possible in humans.

The research, which was published in the journal Nature, may help doctors better predict, identify, and treat illnesses brought on by these viruses, potentially saving lives. The National Heart, Lung, and Blood Institute (NHLBI), a division of NIH, was in charge of the investigation.

It has long been understood by researchers that enteric viruses, such as noroviruses and rotaviruses, may spread through consumption of contaminated food or beverages. It was believed that enteric viruses attack the intestines instead of the salivary gland and then leave the body through faeces. Even while some researchers hypothesised there could be another method of transmission, this hypothesis has mostly gone untested up to this point.

Now, scientists must establish if enteric viruses may spread through saliva in people. The researchers claimed that if they determine that it is, they may also find that this method of transmission is much more widespread than the traditional method. A discovery like that, they suggested, would help explain why the large number of enteric virus infections each year reported globally do not sufficiently take into account faecal contamination as the exclusive route of transmission.

“This is completely new territory because these viruses were thought to only grow in the intestines,” said senior author Nihal Altan-Bonnet, Ph.D., chief of the Laboratory of Host-Pathogen Dynamics at the NHLBI. “Salivary transmission of enteric viruses is another layer of transmission we didn’t know about. It is an entirely new way of thinking about how these viruses can transmit, how they can be diagnosed, and, most importantly, how their spread might be mitigated.”

Altan-Bonnet, who has long studied enteric viruses, claimed that the discovery was entirely accidental. Infant mice are the ideal animal models for studying these infections because of their immature digestive and immune systems, which make them susceptible to infections. Her team had been performing experiments with enteric viruses in these mice.