Suggested Articles Lymphoma Feline Vaccines: Benefits and Risks Diarrhea Neurological Disorders Feline Vision Problems: A Host of Possible Causes Feline Leukemia Virus Feline leukemia virus (FeLV) is one of the most common and important infectious diseases in cats, affecting between 2-3% of all cats in the United States and Canada. Infection rates are significantly higher (up to 30%) in cats that are ill or otherwise at high risk (see below).