 Cat flu is highly contagious and can spread from one feline friend to another via eye, nasal or mouth discharge. Contaminated food or water bowls can also be a source of the spread of disease. Some infected cats don't show any clinical signs, and are known as carrier cats. A carrier is only infectious to other cats when they are shedding the virus, which may be continuous or intermittent. Prevention can be achieved in most households by vaccination. As there are many different strains of the virus, vaccination may not prevent your cat from becoming infected, but will markedly reduce the severity of the disease.