I'm posting this in support of anyone considering taking in a non-aggresive FIV+ cat to be with their own negative cats. I have 5 FIV+ boys and they have been mixing with very young kittens, a very elderly cat, and others for 6 months now, and the only sickness has been the kittens getting colds and ringworm (doubtless from the shelter) and my Siamese coming down with cat flu after escaping into the garden last summer. The FIV boys haven't been sick at all. Dude has stomatatis, he'll always have it, but non-FIV cats get that also. They are all very normal cats.

FIV is carried in saliva and is transmitted through deep bite wounds. It's very fragile, is killed by regular soap and water, and doesn't stay viable for more than a few minutes when away from the body. I suppose I should be concerned that one the the FIV+ boys will leave some drool on a fragment of dry food and, seconds later, one of others will eat it, but I'm more likely to bring in cat flu or FIP on my shoes than something like that happen.

FIV is not a death sentence, to either the cat that carries it or the cats it comes in contact with. With the kind of care we all offer our cats, it shouldn't make any difference to a cat's life. I'm a little more alert with them if they don't eat as well as usual, etc, but that's always turned out to be a false alarm.