Shelters and rescue groups frequently have special adoption requirements for cats who test positive for FIV. Some won't adopt them out to homes with FIV-negative cats, or at all. But a recent study suggests the risks of transmission to other household cats are negligible.
In a study published in The Veterinary Journal, researchers looked at 138 cats co-habiting in a rescue shelter, 8 of whom were FIV-positive. After two series of tests over the years, test results were unchanged, showing "a lack of evidence of FIV transmission, despite years of exposure to naturally-infected, FIV-positive cats in a mixed household."
Additionally, 19 kittens from FIV-positive mothers were also negative, indicating mother-to-kitten transmission did not occur.
Litster A. Transmission of feline immunodeficiency virus (FIV) among cohabiting cats in two cat rescue shelters. Vet J. 2014 Mar 31.