From the Cornell University College of Veterinary Medicine:
It has been estimated that the majority of FIV+ cats never become ill from the virus. From what we have seen, FIV+ cats are more likely to lose their lives because they have tested positive (and no one is willing or able to take them), than because they actually become ill.
From The Best Friends Organization:
FIV FACTS
1. The Feline Immuno-deficiency Virus is a slow virus that affects a cat's immune system over a period of years.
2. FIV is a cat-only disease and cannot be spread to humans or other non-felines.
3. FIV cats most often live long, healthy, and relatively normal lives with no symptoms at all.
4. FIV is not easily passed between cats. It cannot be spread casually - like in litter boxes, water and food bowls, or when snuggling and playing. It is rarely spread from a mother to her kittens.
5. The virus can be spread through blood transfusions, badly infected gums, or serious, penetrating bite wounds. (Bite wounds of this kind are extremely rare, except in free-roaming, unneutered tomcats.)
6. A neutered cat, in a home, is extremely unlikely to infect other cats, if properly introduced.
7. Many vets are not educated about FIV since the virus was only discovered 15 years ago.
8. FIV-positive cats should be kept as healthy as possible. Keep them indoors and free from stress, feed them a high-quality diet, keep and treat any secondary problems as soon as they arise.
2. FIV is a cat-only disease and cannot be spread to humans or other non-felines.
3. FIV cats most often live long, healthy, and relatively normal lives with no symptoms at all.
4. FIV is not easily passed between cats. It cannot be spread casually - like in litter boxes, water and food bowls, or when snuggling and playing. It is rarely spread from a mother to her kittens.
5. The virus can be spread through blood transfusions, badly infected gums, or serious, penetrating bite wounds. (Bite wounds of this kind are extremely rare, except in free-roaming, unneutered tomcats.)
6. A neutered cat, in a home, is extremely unlikely to infect other cats, if properly introduced.
7. Many vets are not educated about FIV since the virus was only discovered 15 years ago.
8. FIV-positive cats should be kept as healthy as possible. Keep them indoors and free from stress, feed them a high-quality diet, keep and treat any secondary problems as soon as they arise.
It would seem the preferable choice would be to house FIV positive cats with other positives, or a one cat household. However there are success stories of FIV positive cats living with normal cats and never passing on the virus.
Here is an example of one very handsome and distinguished gentleman named Grayson:

This handsome cat with a distinguished name has impeccable cat manners
and a wonderful disposition. Grayson was a stray who was unclaimed at
the shelter. He is doing well in our adoption center, and is warm,
safe, and has plenty to eat. The only thing he's missing is the thing
he's never known--a permanent home. He is about 2 years old, very calm,
mellow and extremely friendly. Grayson is FIV positive, so needs to be
in a single cat home, or with other FIV cats. He is very patient and
does well with children. Call (831) 333-0722 if you are interested in
adopting this distinguished boy.






