Zoonotic Diseases: What Pets Can and Cannot Pass to Humans

Human influenza A and B viruses are highly species-specific. While some novel influenza strains — such as certain avian influenza variants — have shown limited capacity to infect humans, the everyday cold and flu your pet may display is caused by entirely different pathogens (such as canine influenza virus or feline herpesvirus) that pose no risk to people. Cross-species transmission of common respiratory viruses between household pets and their owners is not a documented public health concern.

Despite its misleading name, ringworm (tinea) is caused by a group of fungi called dermatophytes. Cats, dogs, and other animals can carry these fungi and transmit them to humans through skin-to-skin contact or shared surfaces. The characteristic ring-shaped rash on human skin is what gave the condition its name — not any parasitic worm. Treatment with antifungal medication is generally effective, but a healthcare provider should confirm the diagnosis.

This is a persistent folk belief with no scientific support. A dog's mouth harbors numerous bacterial species, including Capnocytophaga canimorsus, which can cause severe infections in humans — particularly those who are immunocompromised. While the overall risk from a healthy person receiving a lick on intact skin is low, allowing any animal to contact an open wound is inadvisable and potentially dangerous. Clean wounds with soap and water and consult a healthcare professional if a bite or wound becomes inflamed.

Toxoplasma gondii is a parasite shed in cat feces that can infect humans who handle contaminated litter. Indoor cats may acquire it by eating infected raw meat or prey. While healthy adults typically clear the infection without serious illness, toxoplasmosis poses significant risks during pregnancy. Pregnant individuals are advised by health authorities to avoid cleaning litter boxes or to wear gloves and wash hands thoroughly if unavoidable. Regular litter box hygiene — scooping daily and washing hands afterward — substantially reduces exposure risk.

Rabies is serious and almost always fatal once symptoms appear in humans — which is why post-exposure prophylaxis must begin promptly after any potential exposure. However, casual proximity to a wild animal does not constitute exposure. The virus is present in saliva and neural tissue and requires a break in the skin or contact with mucous membranes to infect a new host. That said, any potential contact with a bat — including waking to find one in a room — warrants immediate medical consultation, as bites from bats can be small enough to go unnoticed. Keeping your pets' rabies vaccines current is one of the most important safeguards, as covered in pet vaccination guidance.