Could Humans Get The Norovirus From Dogs?

New findings published in the Journal of Clinical Microboilogy show that humans can get infected by the norovirus via their canine companions, which is the leading cause of food-borne illness in the United States.

"This strongly suggests that these dogs have been infected with the virus," said first study author Sarah Caddy, VetMB, PhD, MRCVS, a veterinarian and PhD student at the University of Cambridge, and Imperial College, London, UK, in a news release. "We also confirmed that that human norovirus can bind to the cells of the canine gut, which is the first step required for infection of cells."

For the study, researchers examined non-infectious human norovirus particles that consisted solely of the virus' outer protein, called the capsid, which is part of the virus that binds to host cells and is non-infectious because it lacks genetic material.

However, researchers are not certain yet just how much of a problem canine infection and transmission may represent for humans. Despite the dogs' apparent susceptibility, the investigations failed to find norovirus in canine stool samples, even in dogs that had diarrhea. For instance, they found it in serum samples of only about one seventh of 325 dogs tested.

In addition, it is not yet known whether the human norovirus can cause clinical disease in dogs. And for dogs who are infected with the human norovirus, researchers are uncertain if they could shed the virus in quantities that are sufficient to infect humans. Or whether dogs play a role in the epidemiology of some outbreaks of the human norovirus.

"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," concluded Caddy. "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."

Statistics show that 19-21 million Americans are infected with the norovirus annually, which causes vomiting and diarrhea and is extremely contagious. Many of the infections have resulted in over 71,000 hospitalizations and as many as 800 deaths in more severe cases.

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