Cat Infections That Can Spread to Humans

While cats are generally safe, contact with cats, including cat bites and scratches, can cause infections in humans. If you are exposed to a cat, it is important that you understand the potential infections and how to stay safe.

Ringworm

Cats can get ringworm (dermatophytosis)—which is a fungus (not a worm at all). The clearest and most common clinical signs of feline ringworm include the following: circular areas of hair loss, broken and stubbly hair, scaling or crusty skin, alterations in hair or skin color, inflamed areas of skin, excess grooming and scratching, infected claws or nail beds, and dandruff.

In humans, ringworm causes scaly, red, ring-shaped patches on the skin.

A child picking up a cat that has ringworm can easily catch it, and this is the most common infection can acquire from animals.

Cats spread ringworm more often than dogs. This fungal infection is more likely to affect kittens, older cats, or cats who are otherwise sick. Long-haired cats or cats who live with multiple other cats are also at higher risk.

Salmonella: Typhoid Kitty?

Cats can spread salmonella to humans. This infection may cause fevers, abdominal pain, vomiting, diarrhea, and other symptoms in humans. Cats may not have any symptoms from salmonella, so handlers may not realize the risk.

Cats are thought to be at risk of getting salmonella from the birds they catch or by eating other raw meat. It can also be spread through contaminated food. For example, an outbreak of salmonella in humans was associated with dry cat (and dog) food. It affected young children in homes where cats and dogs were fed in the kitchen.

Toxoplasmosis

Cats can spread Toxoplasmosis, a parasitic infection, to humans. Cats can acquire Toxoplasma by eating infected rodents, birds, or anything contaminated with feces from another infected animal.

The infection is usually self-limited. It may feel like the flu and cause swollen glands. In some people, it can cause long-term blurry vision and eye pain. 

If this infection is newly acquired during pregnancy, it can cause serious birth defects. It can be very serious for people who are immunocompromised, and it can cause a brain infection in people who have AIDS. One small study suggested that the infection could be associated with psychological effects in humans.

Cats are part of the parasite's lifecycle. If they are carriers (often transiently as kittens), they will shed Toxoplasma gondii in their kitty litters.

You can get this infection by eating without washing after cleaning the kitty litter. The infection can spread from a person's hands through meat, vegetables, or other food if contaminated debris from cat droppings is not washed off. 

Q fever

Q fever is a rare infection; in 2017, 153 acute cases and 40 chronic cases of Q fever were reported in the United States. Possibly half of those infected do not have any symptoms. This infection can cause high fevers, severe headaches, body aches, and abdominal pain. It can be serious and may cause pneumonia and, rarely, heart valve infections.

It is caused by a bacterial infection due to Coxiella burnetii. The bacteria can be inhaled with dust in the air, and it is spread when an infected mother cat is giving birth.

Influenza

You sneeze. Your cat sneezes. There's a tiny, tiny chance your cat got what you got but usually, cats do not become sick with the flu in the same way that humans do. 

One Ohio study showed that 62% of 400 tested domestic cats showed signs of past flu. The H1N1 pandemic infected 30% of domestic cats that were studied in Northern China. This, however, has not been shown to have any real effects on cat owners.

Toxocara

A cat may treat the backyard as its kitty litter. As a result, Toxocara worm eggs (Toxocara cati) may be released into the soil.

These larvae may penetrate and migrate under the skin, with resultant inflammation, itching and pain, and raised, red linear lesions in the skin that follow the larva’s migration. Proper hygiene, including washing hands before meals, cleaning soil from vegetables, and reducing exposure to cat feces can prevent infection. Anti-parasite medications for kittens and annual fecal exams for adult cats can reduce environmental contamination and the risk of human infection.

Perhaps 1 in 4 cats carry this infection.

Humans—especially children—may accidentally put their hands in their mouths after touching contaminated dirt. Most people who are exposed do not develop symptoms. But exposure can lead to Visceral Larva Migrans, with worms spreading internally (and causing high eosinophil blood cell levels). The infection can also cause Visceral Ocular Migrans, with resulting vision loss and eye damage.

This is very, very rare, but it has been reported. In 2014, 2 people in England developed active Tuberculosis (TB) and 2 people were found to have had latent TB (no active disease despite the bacteria's presence in the body) from exposure to cats.

Having a cat or being in contact with a cat means that you need to be aware of how to keep yourself and your cat free of potentially harmful infections. The more you learn about proper cat care, the more you can avoid illness and enjoy your time with your cat.