Norovirus infections suck. I know from personal experience.

Sometimes incorrectly referred to as the stomach flu (since it has nothing to do with influenza), norovirus infections in most otherwise healthy people tend to be fairly short-lived, but they still make you feel miserable (to say the least).

Previous studies have suggested that dogs can sometimes be infected with noroviruses, but data have been limited. So, my general recommendation has been to just try to avoid puking on your pet. Less dramatic contamination of a pet’s haircoat (e.g. you have norovirus on your hands and you pet the dog/cat, and then someone else pets the same animal) probably also poses some risk of transmission between people, just like inanimate objects that have been touched. However, I haven’t been too concerned about dogs actually getting infected themselves and then infecting people.

A recent paper in Emerging Infectious Diseases (Charoenkul et al. 2020) adds a twist to the situation. It describes an outbreak of gastrointestinal (GI) disease in kids and dogs in a household.

Two young kids got sick first and were diagnosed with norovirus. Shortly thereafter, two dogs were moved from the family’s kennel into the household. Those two dogs, plus 5 of 6 puppies from a litter born in the household developed GI disease a short time after the kids got sick. Norovirus was found in fecal samples from the puppies and adult dogs in the household. Some dogs were positive for three weeks, which makes it more likely that they were truly infected (i.e. the virus was replicating in the dog), rather than the test simply detecting norovirus particles that had been ingested and were just passively moving through the dog’s intestinal tract and came out the other end. No other typical causes of canine diarrhea were identified. That doesn’t guarantee the problem was norovirus, but it makes it more likely.

When they looked at the genetic makeup of norovirus in the two human samples vs the two canine samples, the viruses from the dogs “clustered” with the human viruses, and they were all consistent with the typical human norovirus, not the noroviruses previously reported in dogs (see image below). This all makes it most likely that the human and canine infections were linked, and that people were the source.

Is this a big deal?

  • Probably not. However, it provides more evidence that dogs can sometimes be infected with human norovirus.  Since the virus was detected in the dogs’ feces, it raises the potential that they could then infect people.
  • While it’s not a game-changer, it’s still interesting and shows the importance of basic hygiene (especially handwashing) when you’re sick, remembering that pets can be part of the family microbiologically, as well as socially.