This article is from the Feline Leukemia (Cats) FAQ, posted to rec.pets.cats newsgroup. Maintained by Erin Miller with numerous contributions by others.
Some of these points are mentioned in the general section above, but here are more specific questions geared to people whose cats have tested positive. The most important point to stress is that FeLV+ cats *MUST* be made indoors-only. This needs to be done for two reasons. First, the more you expose your cat to outside ills, the more likely it is to contract an FeLV-related disease or infection. The second reason is that FeLV+ cats are like Typhoid-Marys to any other cat they meet. As noted above, the vaccine is only 75-85% effective, so any vaccinated cat that your cat encounters is at risk, as well as any unvaccinated cat. If these cats are then infected and they continue to interact and infect other cats, then you could give rise to an epidemic in your area. If you cannot or will not keep your FeLV+ cat indoors, than the only humane thing to do is find a home for it with someone who will (ways to do this are suggested below), or have your cat put to sleep. This may sound extreme, but it is extremely selfish to allow your cat to roam the neighborhood possibly infecting all the local outdoor cats just because you refuse to keep your cat indoors. Keeping your cat indoors is one of the responsibilities of owning an FeLV+ cat.