Danger to Humans

Usually cats are not aggressive to people, but they might scratch or bite when they are playing.

As a prevention wounds caused by cats should be cleaned with an antiseptic. Scratches can infect. If this happens to you then you should go to a doctor.

Symptoms of fever after being scratched by a cat can mean fever-of-cats.

Rabies

The saliva of cats, alike what happens with other animals, can transmit rabies. If bitten by a cat, and you live in an area where there may be rabies, you should seek a doctor immediately.

Toxoplasmosis

Other diseases and infections may be transmitted to humans, such as toxoplasmosis, which can be present in the feces of cats. Unlike the rabies, these diseases are not serious, but you should maintain good rules of hygiene. Toxoplasmosis, that is a disease of which Toxoplasma gondii is the causative agent, can be dangerous for pregnant women.

Hygiene

To minimize the risks of getting an infection there are important rules of good hygiene, in handling/cleaning the litter box, and keeping the objects that are in contact with the cat, as his bed (or the place where he sleeps), cleaned. And if the cat shows signs of an infection, these objects should be disinfected.