Feline leukemia virus (FeLV) infection is responsible for more deaths among cats than any other infectious disease. FeLV is capable of producing a wide variety of associated diseases and symptoms. Degenerative diseases, such as anemia, liver disease, intestinal disease and reproductive problems can be seen. In other cats, the virus produces cancerous diseases, such as lymphosarcoma and leukemia. Many cats suffer from suppression of the immune system and other illnesses, depending on which organ is involved.