Illustration of a rotavirus structure. Credit: Getty Images
An international research team has discovered that rotaviruses and noroviruses, which are known to cause infection via the fecal-oral route, can also proliferate in salivary glands and spread through saliva1.
The researchers say this means new strategies will be needed to prevent this route of transmission.
Rotaviruses mainly affect children under five in developing countries; whereas noroviruses still infect people in developed countries. The viruses replicate in the intestine and cause vomiting and diarrhoea. Recent outbreaks of norovirus in the USA and Europe, where hygiene awareness is high, raise the possibility of a transmission route other than fecal-oral.
To better understand this, scientists orally infected mouse pups with the viruses. These pups were then breastfed by non-infected mice. The researchers found a surge of antibodies specific to the viruses in the mothers’ milk and traces of viral RNA in their mammary glands. This indicates that the mothers were infected with the viruses during breastfeeding.
The team, which included Sourish Ghosh who is an expert on infectious diseases at the CSIR-Indian Institute of Chemical Biology in Kolkata, found that the viruses replicated in the salivary glands of the pups and reached the mothers via saliva backflow during suckling. The viruses lingered for a long time in the salivary glands of healthy mice and even longer in mice with weakened immune systems.
The researchers say the salivary glands may act as reservoirs, spreading the viruses via saliva in the absence of diarrhoea. This means cross-infection could happen when people cough, sneeze or talk near others. Their findings suggest that new sanitation measures – in addition to existing steps to prevent fecal spread – may be needed to prevent transmission through saliva.
