Dogs can catch several types of infections from humans, including influenza, COVID-19, norovirus, MRSA, tuberculosis, and ringworm. This human-to-animal disease transmission, sometimes called reverse zoonosis, is more common than scientists once believed. Influenza and coronaviruses make up the majority of documented cases in pets.
Respiratory Infections
The H1N1 strain of influenza (swine flu) is one of the best-documented examples of a virus jumping from humans to dogs. During peak flu seasons, dogs living as household pets show higher infection rates than farm dogs or strays, likely because of more frequent and prolonged close contact with sick owners. Interestingly, many infected dogs never develop visible symptoms, which means your dog could pick up the virus and carry it without you ever realizing anything is wrong.
When dogs do show symptoms from a human-origin respiratory virus, the signs look similar to what you’d expect from canine flu: coughing, runny nose, fever, lethargy, eye discharge, and reduced appetite. Most dogs recover within two to three weeks, though a small number develop secondary bacterial infections that can progress to pneumonia.
COVID-19
The virus that causes COVID-19 can spread from people to dogs during close contact. Dogs and cats worldwide have tested positive, mostly in households where an owner was actively infected. The good news is that serious illness in pets is extremely rare. Most dogs that do get sick experience only mild symptoms and recover fully. There’s currently no evidence that dogs play a meaningful role in spreading the virus back to other people, but limiting close contact with your pets while you’re sick remains a reasonable precaution.
Norovirus and Stomach Bugs
Human norovirus, the common cause of sudden vomiting and diarrhea outbreaks in people, can also infect dogs. In 2018 in Thailand, a recombinant norovirus strain was detected in dogs with diarrhea living on the same premises as infected children. Genetic sequencing confirmed the canine and human viruses were nearly identical, pointing strongly to human-to-dog transmission. Earlier cases in Finland found the same pattern with different norovirus variants.
Affected dogs developed fever, acute watery diarrhea, and mild dehydration. Puppies were hit harder than adult dogs: five out of six puppies in the Thai outbreak showed clinical signs, compared to two out of eighteen adult dogs. If your household is dealing with a stomach virus and your dog develops diarrhea around the same time, there’s a real possibility the two are connected.
MRSA
MRSA, the antibiotic-resistant staph bacteria, passes between humans and dogs primarily through direct skin-to-skin contact. It can also spread through contaminated objects like wound bandages. Dogs living in close contact with people who are infected or colonized with MRSA can become colonized themselves. This creates a frustrating cycle: a person clears their MRSA infection with treatment, but their dog has been silently carrying the bacteria and reintroduces it back into the household. If you’re dealing with recurring MRSA infections, your veterinarian can test your dog to see if they’ve become a carrier.
Ringworm
Ringworm is a fungal skin infection, not a worm, and it moves easily between humans and animals in both directions. The fungal spores can begin invading skin and hair within six to eight hours under the right conditions. Transmission happens through direct contact, but simply touching an infected person or surface doesn’t guarantee infection. The fungus needs enough spores present, some degree of skin damage (even tiny scratches), and moisture on the skin to take hold. Dogs with ringworm typically develop circular patches of hair loss with scaly, crusty skin.
Tuberculosis and Mumps
Tuberculosis has been documented passing from humans to dogs, though it’s uncommon in countries where TB rates are low. Dogs living with a person who has active tuberculosis are at the highest risk, particularly in settings with poor ventilation and prolonged exposure.
Mumps is a more unusual case. Research has found antibodies to the mumps virus in dogs, confirming that the virus can infect them. However, infected dogs don’t appear to actually get sick from it. And since mumps cases have declined by 99 percent in the United States thanks to vaccination, the chance of passing it to your dog is vanishingly small.
Why Many Cases Go Unnoticed
One of the challenges with reverse zoonosis is that dogs often carry human pathogens without showing obvious illness. Studies on H1N1 in dogs specifically highlighted this problem: researchers found significant infection rates in dogs that appeared completely healthy. Standard veterinary testing typically screens for three or four pathogens at a time and can miss infections caused by human-origin viruses that aren’t part of routine panels. Newer diagnostic approaches using advanced DNA sequencing can identify a much wider range of pathogens in a single test, but these aren’t yet standard in most veterinary clinics.
Reducing Your Dog’s Risk
The practical takeaway is straightforward. When you’re sick, the same hygiene measures that protect other people in your household also protect your dog. Avoid letting your dog lick your face or hands. Wash your hands before handling their food or toys. If possible, have someone else in the household take over feeding and walking duties while you’re symptomatic. This applies especially to respiratory infections and stomach viruses, which account for the bulk of documented human-to-dog transmission.
Dogs that sleep in their owner’s bed, share food, or receive frequent face-to-face contact are at higher risk simply because of the volume of exposure. You don’t need to quarantine yourself from your pet during every cold, but during confirmed flu, COVID-19, or a norovirus episode, a few days of reduced contact can make a real difference.