Could your dog give you norovirus?

13 Apr

Norovirus is the leading cause of foodborne illness in the US. You can also catch

it from infected people and contaminated surfaces. Now, new research raises the question

of whether humans can catch it from dogs.

dog and young girl
The study raises enough evidence for further investigation into whether dogs can pass norovirus onto humans.

Writing in the Journal of Clinical Microbiology, veterinarian Sarah Caddy and

colleagues explain how they found some dogs can mount an immune response to human

norovirus – a strong clue that they have been infected by the bug.

Caddy, who is working toward her PhD at the University of Cambridge and Imperial

College London in the UK, says:

“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.”

Together with evidence that human norovirus has been isolated from domestic dogs in

Europe, the findings raise concerns that people could catch the bug from animals.

Norovirus is a leading cause of gastroenteritis, or “stomach flu,” causing vomiting and

diarrhea in both adults and children. It is very contagious and can infect anyone. You

can catch it from an infected person, contaminated food or water, or from contaminated


According to the Centers for Disease Control and Prevention (CDC), in the US every

year norovirus is responsible for 19-21 million cases of acute gastroenteritis and

contributes to 570-800 deaths, mostly among young children and the elderly.

Human norovirus particles can bind to dog intestinal tissue

For their study, Caddy and colleagues used noninfectious human norovirus particles –

comprising just the bug’s outer protein coat, or capsid. The capsid is the part of the

virus that binds to host cells. Capsids alone cannot cause infection because they lack

the internal machinery of the virus.

The team studied the ability of capsids to bind to tissue samples from dog intestines

in test tubes. They found evidence that seven different strains of human norovirus may be

able to bind to canine gastrointestinal tissue. This suggests “that infection is at least

theoretically possible,” they note.

The researchers also carried out other tests to discover if dogs can carry human


While they found 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.

It is currently not known whether human norovirus can cause clinical disease in dogs.

Assuming that it can, the study found no evidence that dogs can shed it in sufficient

quantities to infect humans. However, the authors note that other studies have suggested

as few as 18 virus particles can cause human infection.

There is also little evidence that dogs or animals are involved in spreading norovirus

among people when large outbreaks occur, such as on cruise ships and in hospitals.

Evidence from this study is sufficient to warrant further investigation

Nevertheless, the authors conclude that their study provides sufficient evidence to

warrant further investigation into whether human norovirus can survive in nonhuman animals

and spread from them to people.

Caddy says she got interested in doing the study through her experience as a small

animal veterinarian and dog owner. She says in her practice, dog owners often ask her if

their dogs can pass infections onto them or whether they can pass them to their pets. She


“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


Meanwhile, Medical News Today recently learned that a drug-resistant intestinal bug is spreading in US. A

CDC report suggests a multi-drug

resistant strain of Shigella – a bug that causes half a million cases of

diarrhea in the US every year – is entering the country in infected travelers and causing

a series of outbreaks.