Cats can be infected or infested with viruses, pathogenic bacteria, fungus, protozoans, arthropods or worms that can transmit diseases to humans; infections of most concern include salmonella, cat-scratch disease, and toxoplasmosis.[247]

In some cases, the cat exhibits no symptoms of the disease.[248] The same disease can then become evident in a human.[249] The likelihood that a person will become diseased depends on the age and immune status of the person. Others might also acquire infections from cat feces and parasites exiting the cat’s body.[247][250]