This article is from the Feline Infectious Peritonitis FAQ, posted to rec.pets.cats newsgroup. Maintained by Erin Miller with numerous contributions by others.
People often use the "it's like AIDS" phrase to describe a number of illnesses in the animal (and human) community with the idea that most people know so much about AIDS that this analogy is useful. Unfortunately most people don't know much about AIDS and the resulting effect is to scare people out of their wits and have them dump their cats or dogs at the nearest pound because they are so deathly afraid of catching AIDS from them. The ONLY similarity between FIP, FIV (Feline Immunodeficiency Virus) and FeLV (Feline Leukemia Virus) to HIV (which is believed to cause AIDS) is in their genetic makeup. All are RNA (as opposed to DNA) viruses, and FeLV and FIV (and HIV) are what are known as "retroviruses." FIP is a type of "coronavirus" which makes it even less similar to HIV. To make it clear: THERE IS ABSOLUTELY NO WAY TO CATCH AIDS FROM A CAT, NO MATTER WHAT FELINE DISEASE THAT ANIMAL MAY HAVE. See the FeLV FAQ for more information on retroviruses.