What is a "latent" carrier?
In some feline leukemia carriers, the virus may retreat temporarily, hiding in the cat's bone marrow. In this stage, the virus is dormant; the cat is not contagious and does not have to constantly fight the virus. These latent carrier cats live normal lives until the virus re-emerges.
Stress often causes the virus to come out of the bone marrow and renew its attack. If a cat doesn't eat a proper diet, if it becomes ill or if something makes it constantly nervous (like the presence of a rival cat), the cat is under stress. Because the immune system does not function as well when stressed, the virus may choose that time to pop out and start fighting again. In both carriers and latent carriers, stress may weaken the cats' systems enough to allow FeLV to completely affect the cats' bodies.