Norovirus—the word alone might be enough to make you a little nauseous. According to the United States Center for Disease Control and Prevention (CDC), noroviruses (there are many types) are the “leading cause of illness and outbreaks from contaminated food in the United States.” People can also become infected with norovirus through touching contaminated surfaces or by having contact with someone who is infected with norovirus. The CDC estimates that as few as 18 virus particles may be enough to cause illness in people, which explains why norovirus infections (often mistakenly called the “stomach flu”) tend to be highly contagious, rampaging their way through homes, schools, businesses, cruise ships, etc.
The symptoms of norovirus infection in people are downright nasty. Vomiting, diarrhea, fever, headache, and body aches are common and tend to last anywhere from one to three days. If you’ve lived with dogs for long enough, you’ve probably observed them having similar symptoms, perhaps even right before, during, or after you’ve been sick. Under these circumstances, it’s reasonable to wonder if dogs can get norovirus and, if so, whether the virus can be passed between people and dogs.
First, some clarification is needed. Dogs (and cats) appear to have several of their own species of norovirus that cause gastrointestinal symptoms similar to those described above. The question we’re asking here is whether or not viruses that we’ve assumed can only infect one species (or closely related species) can actually move between dogs, cats, people, etc. Why is this important? If it proves to be true, we would know that when dogs in a household become infected with norovirus, people could be at risk for infection, and vice versa.
A few scientific papers have recently been published that attempt to answer this question.
In 2012, a group of researchers in Helsinki, Finland looked at 92 stool samples from dogs living closely with people who had recently experienced symptoms of vomiting and diarrhea. They screened those samples for several different types of human norovirus and found human norovirus in “four faecal samples from pet dogs that had been in direct contact with symptomatic persons…. All NoV [norovirus]-positive dogs lived in households with small children and two dogs showed mild symptoms.”
The study’s authors concluded that human noroviruses “can survive in the canine gastrointestinal tract. Whether these viruses can replicate in dogs remains unresolved, but an association of pet dogs playing a role in transmission of NoVs that infect humans is obvious.”
Another interesting paper appeared in 2015 and was titled “Evidence for Human Norovirus Infection of Dogs in the United Kingdom.” The research showed that human norovirus could indeed bind to canine gastrointestinal tissues and that 13% of the dogs in the study had antibodies against human norovirus in their bloodstream, an indication that they had been previously infected. Interestingly, the types of human noroviruses that the dogs had been infected with closely mirrored the types of noroviruses that had been circulating in people in their communities.
While the scientists did not find evidence that human norovirus could be transmitted through dog feces, this study does show that it is at least theoretically possible for dogs to act as a reservoir for human norovirus.
Since then, there have been no further reports of human norovirus infections in dogs (or cats), but this certainly is a topic that deserves more attention. And until we know for sure whether noroviruses have the ability to move between species, it only makes sense to practice meticulous hygiene if anyone in the family develops vomiting or diarrhea.
Emory University: Norovirus stays infective for months in water
Pet dogs--a transmission route for human noroviruses? Summa M, von Bonsdorff CH, Maunula L. J Clin Virol. 2012 Mar;53(3):244-7.
Evidence for human norovirus infection of dogs in the United Kingdom. Caddy SL, de Rougemont A, Emmott E, El-Attar L, Mitchell JA, Hollinshead M, Belliot G, Brownlie J, Le Pendu J, Goodfellow I. J Clin Microbiol. 2015 Jun;53(6):1873-83.