Cats can carry at least 16 diseases that spread to humans, ranging from common infections like ringworm and cat scratch disease to serious ones like rabies and toxoplasmosis. Most of these are preventable with basic hygiene and routine veterinary care, but understanding the risks helps you protect yourself, especially if you’re pregnant or have a weakened immune system.
Bacterial Infections
Cat scratch disease is one of the most well-known cat-to-human infections. It’s caused by bacteria that live in fleas and get into a cat’s claws or saliva. A scratch or bite introduces the bacteria into your skin, and within a few days to weeks you may notice swollen lymph nodes, fever, and fatigue near the wound site. Most healthy adults recover without treatment, but the infection can become serious in people with compromised immune systems.
Salmonella and Campylobacter are gut bacteria that cats can shed in their feces, often without showing any symptoms themselves. You pick these up by accidentally touching contaminated litter or surfaces and then touching your mouth. Both cause diarrhea, cramping, and fever that typically resolve within a week.
MRSA (antibiotic-resistant staph) can pass between cats and their owners in both directions. Cats may carry it on their skin or in their nose without appearing sick, and close contact, especially around open wounds, creates a transmission route.
Two rarer bacterial diseases also appear on the CDC’s list. Plague, while uncommon, still occurs in the western United States, and outdoor cats that hunt rodents can bring infected fleas into the home or develop the infection themselves. Tularemia spreads similarly through contact with infected animals or tick bites.
Toxoplasmosis and Pregnancy
Toxoplasmosis gets the most attention among cat-related infections, and for good reason. Cats are the only animal that sheds the infectious form of the parasite in their feces. Once shed, the parasite becomes infectious within 1 to 5 days. You can pick it up by cleaning a litter box without gloves, gardening in contaminated soil, or eating unwashed produce from a garden where cats have been.
Most healthy people who get toxoplasmosis never notice it. The real danger is during pregnancy: a woman newly infected during or just before pregnancy can pass the parasite to her unborn child, potentially causing serious developmental problems. The FDA recommends that pregnant women have someone else handle litter box duties if possible, scoop the litter daily (before the parasite has time to become infectious), wear gloves when gardening, feed cats only commercial food, keep indoor cats indoors, and avoid adopting a new cat until after delivery. Rehoming your existing cat is not necessary.
It’s worth noting that most human toxoplasmosis infections actually come from undercooked meat, especially pork, lamb, and venison, not from cats. Contaminated shellfish and unpasteurized goat’s milk are also sources. Cat ownership is one risk factor among several.
Parasites: Worms and Protozoa
Cats commonly carry several intestinal parasites that can infect humans. Roundworm is the most concerning. When roundworm eggs from cat feces are accidentally swallowed (usually by young children playing in contaminated soil or sandboxes), the larvae can migrate through the body. In what’s called visceral larva migrans, the larvae travel to the liver, lungs, or muscles, causing fever, coughing, weight loss, and rashes. This occurs mostly in preschool-aged children. In rarer cases, larvae reach the eye, where they can cause permanent vision loss or blindness, typically affecting one eye in older children or young adults.
Hookworm larvae from cat feces can burrow through bare skin, usually on the feet, causing an intensely itchy, winding rash. Cat tapeworm spreads differently: humans (usually children) get infected by accidentally swallowing an infected flea, which is why flea control matters for more than just comfort.
Two waterborne parasites, Cryptosporidium and Giardia, also appear in cat feces and cause watery diarrhea in humans. These are more of a concern in households with immunocompromised members, where even mild infections can become prolonged and dangerous.
Rabies
Cats are the most frequently reported rabid domestic animal in the United States, with roughly 200 to 300 cases reported each year. This doesn’t mean cats are inherently more susceptible than dogs. It reflects the fact that many cats roam outdoors and are less consistently vaccinated. Rabies is virtually always fatal once symptoms appear, making vaccination the single most important thing you can do for any cat that goes outside or could encounter wildlife. Even indoor cats should stay current on rabies vaccines, since bats can enter homes.
Ringworm and Skin Infections
Ringworm is not a worm at all but a fungal infection of the skin. Cats, particularly kittens, are frequent carriers and can spread it through direct contact or by shedding fungal spores onto furniture, bedding, and clothing. In humans, it shows up as a red, circular, itchy patch on the skin. It’s highly contagious but treatable with antifungal creams or oral medication. Cats themselves may show patchy hair loss and scaly skin, though some carry the fungus without visible symptoms.
Sporotrichosis is a rarer fungal infection that cats can transmit through scratches or bites. It causes skin nodules that can spread along the lymph system and is more common in tropical and subtropical climates.
Who Faces the Greatest Risk
For most healthy adults, the risk of catching a serious illness from a pet cat is low. The people who need to take extra precautions fall into a few groups: pregnant women, young children (especially under five), older adults, and anyone with a weakened immune system from conditions like cancer, HIV, diabetes, or immunosuppressive medications.
People without a functioning spleen are at particular risk from bacteria in cat saliva. An infection called Capnocytophaga, found naturally in the mouths of cats and dogs, rarely affects healthy people but can cause sepsis, kidney failure, and gangrene in immunocompromised individuals after a bite or close contact with saliva on broken skin.
Reducing Your Risk
Consistent flea and tick prevention is one of the most effective things you can do. In laboratory studies, cats on proper flea control were completely protected from the bacteria that causes cat scratch disease. Flea prevention also breaks the transmission cycle for tapeworm, since the parasite requires a flea to develop its infectious stage.
Beyond flea control, practical steps make a significant difference:
- Wash your hands after handling your cat, scooping litter, or touching anything that contacts cat feces.
- Scoop the litter box daily. Most parasites need at least a day in the environment before becoming infectious.
- Keep cats indoors. Indoor cats have dramatically lower exposure to rabies, plague, tularemia, and most parasites.
- Feed commercial food only. Raw meat diets increase the risk of toxoplasmosis and Salmonella in cats.
- Keep veterinary visits current. Regular deworming, flea prevention, and rabies vaccination address the majority of transmission risks.
- Avoid rough play that leads to scratches, and keep your cat’s nails trimmed.
- Cover outdoor sandboxes so cats don’t use them as litter boxes, especially if young children play in them.
If you’re immunocompromised and considering adopting a cat, choose one older than a year. Kittens are more likely to scratch, bite, and carry infections. Have any new cat tested for feline leukemia and feline immunodeficiency virus, and keep the litter box away from areas where you prepare or eat food.