Got the stomach flu? Your dog could be to blame.

Norovirus, the leading cause of gastroenteritis, or stomach flu, affects 23 million people in the U.S. each year, and studies show that we can contract the virus from man’s best friend.

Until last year, it was thought that animals didn’t carry human norovirus because of species barriers. But a study at the University of Helsinki in Finland found that dogs do carry human strains of the virus and can pass them to humans.

Researchers took 92 fecal samples from dogs living in homes where either people or their pooch had recently experienced symptoms of stomach flu such as vomiting or diarrhea. They found human strains of norovirus in four of the samples.

Two of the dogs that tested positive had exhibited symptoms of infection, but researchers say it’s still unclear whether animals can be sickened by human noroviruses.

Where are dogs picking up the virus? Study co-author Carl-Henrick von Bonsdorff says canines likely contract it from sick family members, specifically young children.

However, dogs can also be exposed to norovirus by sniffing, licking or consuming contaminated materials — such as feces, vomit or saliva — outside the home.

But even though your pet could carry the virus, doctors say you’re more likely to get it from a person than a puppy.

Dr. Francine K. Rattner, a veterinarian in Edgewater, Md., says the best way to protect yourself from norovirus is by washing your hands, not sharing food and drink with sick people and keeping pets away from sick children.

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