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What Dogs Can Transmit
Your dog shares more than your couch. A 2015 PubMed review of bacterial and viral zoonotic infections from dogs documented transmission of rabies, norovirus, Pasteurella (from bites or scratches), Salmonella, Campylobacter, Brucella, Capnocytophaga, Leptospira, and MRSA. Each of these has a different transmission route, which matters more than the list itself.
Rabies spreads through bites from infected animals — still the most lethal zoonosis globally, though rare in vaccinated domestic dogs in the US. Salmonella and Campylobacter are fecal-oral: they move from dog waste to your hands to your mouth, usually because hand washing got skipped. Pasteurella lives in the mouths of most healthy dogs and causes serious skin and tissue infections when introduced through a bite or deep scratch. Capnocytophaga, another oral bacterium, is typically harmless — unless you're immunocompromised, in which case it can cause sepsis. Leptospira spreads through urine-contaminated water and soil, making it more of a concern for dogs with outdoor exposure. MRSA is a two-way street covered below.
The CDC's Emerging Infectious Diseases journal frames companion animals as a significant and under-surveilled interface for zoonotic disease under the "One Health" framework — the recognition that human, animal, and environmental health are connected. The concern isn't that pet dogs are walking biohazards. The concern is that the interface gets almost no routine surveillance, so outbreak patterns are often identified late.
A 2025 PMC review comparing pet dogs to strays found that pet dogs' greatest transmission risks come from bites, close-contact infections, and antimicrobial-resistant bacteria — not the environmental pathogens more associated with strays. That's a meaningful distinction. A stray dog rolling in contaminated soil carries different risks than a vaccinated house dog who sleeps in your bed and licks your face.
What the Risk Actually Looks Like in Practice
Most healthy adults with healthy dogs face very low risk from routine contact. The elevated-risk populations are infants, the elderly, pregnant women, and immunocompromised individuals. For these groups, the math changes. A Campylobacter infection that gives a healthy adult a bad week of diarrhea can hospitalize an elderly person or someone on chemotherapy. Capnocytophaga, which most people never need to worry about, has a fatality rate of 30% or higher in people without a functioning spleen.
For high-risk households, the precautions are specific: no face-licking, careful hygiene around dog waste, and keeping the dog's parasite prevention current. Toxocara — roundworm larvae — can migrate to the eyes or brain in children who ingest contaminated soil. It's preventable with regular deworming. It's also the kind of thing most people don't know until it's too late.
It Goes Both Ways
Dogs can catch things from you. MRSA and influenza A (H1N1) both have documented cases of reverse zoonotic transmission — human to dog. MRSA in particular appears to cycle back and forth in households: a person carries it, the dog picks it up, and the dog reinfects the person after treatment. If you're sick, basic hygiene around your dog is reasonable and not paranoid.
Simple Risk Management
Wash hands after handling dog waste and before eating — this covers most fecal-oral transmission routes in one step
Keep vaccinations and parasite prevention current; lapsed prevention is where most of the actual risk lives
Treat bites and scratches immediately — Pasteurella can progress to a serious infection within hours, not days
Don't let dogs lick wounds, eyes, or mouth
Regular vet checkups can catch carrier status before transmission occurs; dogs can shed Salmonella without showing any symptoms
