Feline Immunodeficiency Virus, a close relative to HIV which causes an AIDS-like condition in cats. It is not transmittable to humans, though cats can transmit it to each other through bites, scratches, and other transfers of bodily fluids.
A veterinarian can administer a blood test to check for the presence of FIV antibodies, similar to the human test for HIV. Kittens should be tested as part of their first veterinary exam, along with the test for feline leukemia.
There is presently no cure for FIV.