Could Man's Best Friend Spread Norovirus?

Norovirus, the leading cause of acute gastroenteritis in adults and children in the US (aka "stomach flu” marked by vomiting and diarrhea) could potentially be spread from canines to humans, according to research published in the Journal of Clinical Microbiology.

According to the Centers for Disease Control and Prevention (CDC), norovirus is the primary cause of approximately 19-21 million incidences of acute gastroenteritis and is responsible for nearly 570-800 deaths in the US annually — mainly among young children and the elderly.

Sarah Caddy, MD, veterinarian and PhD candidate at the University of Cambridge and Imperial College London, UK, and her colleagues shared how they realized some dogs can post an immune response to human norovirus.

Caddy and colleagues used noninfectious human norovirus particles - comprising just the bug's outer protein coat (capsid), which binds to host cells. Lacking the framework of the virus, capsids, alone cannot cause infection, so the team observed the capsids’ ability to bind to tissue samples from dog intestines in test tubes.

Evidence revealed that 7 different strains of human norovirus could bind to canine gastrointestinal tissue, which suggested, "That infection is at least theoretically possible.”

Researchers took it a step further, carrying out other tests to look at whether dogs were capable of carrying human norovirus. Although they reported no trace of virus in stool samples from 248 dogs (including some with diarrhea), they did find evidence of antibodies to human norovirus in blood samples from 43 out of 325 dogs.

Caddy said, "We also confirmed that human norovirus can bind to the cells of the canine gut, which is the first step required for infection of cells."

There’s currently no evidence indicating whether human norovirus can cause clinical disease in dogs or that dogs or animals are involved in spreading norovirus among people when large outbreaks occur, such as on cruise ships and in hospitals. However, the authors expressed that prior studies noted that it only would take as few as 18 virus particles to trigger human infection.

Nevertheless, the authors understand further research is imperative to investigate whether “human norovirus can survive in nonhuman animals and spread from them to people”.

Caddy concluded, “There are plenty of anecdotal cases of dogs and humans in the same household, having simultaneous gastroenteritis, but very little rigorous scientific research is conducted in this area. Until more definitive data is available, sensible hygiene precautions should be taken around pets, especially when gastroenteritis in either humans or dogs is present in a household.”