Noroviruses are a type of virus that cause serious diarrheal diseases such as acute gastroenteritis, an inflammation of the stomach or intestines with symptoms such as diarrhea and vomiting, which occurs annually in some 685 million people in the world and which causes the death of about 50,000 children each year, according to the Centers for Disease Control and Prevention (CDC).
Norovirus and other stomach viruses, which are also responsible for the widespread outbreaks that sometimes occur on vacation cruises, can grow in the salivary glands of mice and spread through their saliva, a team of scientists has just discovered. scientists from the US National Institutes of Health (NIH).
The fact that these pathogens – which are called enteric viruses – are transmitted through saliva suggests that talking, coughing, sneezing, sharing food, cutlery and other utensils that come close to the mouth, or kissing, have the potential to spread viruses, although as the finding has been in mice, it is necessary to carry out studies to confirm that this also occurs in people.
The results of the new study have been published in the journal Nature and may prove useful in finding new and better ways to prevent, diagnose and treat diseases caused by these viruses and thus save lives, which could save lives.
Better prevent and treat norovirus infections
It has long been known that enteric viruses such as noroviruses and rotaviruses can be spread by ingesting food or drinks contaminated with fecal matter that contains them, but it was believed that these viruses did not stop at the salivary gland, but went directly to the intestines and then excreted in the feces. Although some scientists suspected that there could be another route of transmission, until now this hypothesis had not been verified.
“Salivary transmission of enteric viruses is a whole new way of thinking about how these viruses can be transmitted, how they can be diagnosed and how their spread can be mitigated”
In fact, the discovery occurred by chance. Nihal Altan-Bonnet, head of the Host-Pathogen Dynamics Laboratory at the National Heart, Lung, and Blood Institute (NHLBI), part of the NIH, and his team had conducted experiments with enteric viruses in infants. mouse, which are the animal models indicated to study these infections because, having immature digestive and immune systems, they are susceptible to infections.
The researchers administered norovirus or rotavirus to a group of mouse pups that were less than 10 days old, then returned them to their cages to nurse from their virus-free mothers. Within a day, one of the study’s authors, Sourish Ghosh, observed that the baby mice had an increase in IgA antibodies – which are key to fighting disease – in their intestines. Considering that the immune systems of the pups were immature, it was not expected that they would generate antibodies yet.
In addition, Ghosh found that the viruses replicated in the mammary tissue of mother mice, and when he collected milk from their breasts, he found that the timing and levels of the IgA surge in breast milk matched the timing and levels of the IgA surge. in the intestines of their young. Infection in the mothers’ breasts appeared to have increased the production of virus-fighting IgA antibodies in their breast milk, helping to clear the infection in their offspring, the researchers said.
New experiments were carried out to find out how the viruses were introduced into the mammary tissue of the mice. They collected samples of saliva and salivary glands from the mouse pups and found that the salivary glands replicated these viruses at very high levels and that they reached the saliva in large quantities. With other tests they confirmed that suckling had caused the transmission of the virus, both from the mother to the calf, and from the calf to the mother.
It now needs to be confirmed whether salivary transmission of enteric viruses is also possible between people, although, if so, this could explain the large number of enteric virus infections that occur each year worldwide, as it seems excessive if contamination fecal is the only route of transmission.
“Salivary transmission of enteric viruses is another layer of transmission that we did not know about. It is a completely new way of thinking about how these viruses can be transmitted, how they can be diagnosed, and more importantly, how their spread can be mitigated,” said Nihal Altan-Bonnet.
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