Feline immunodeficiency virus (FIV) is a member of the retrovirus family. This virus is found all over the world and has been present in the United States since 1968. Like feline leukemia virus and other related family members such as human immunodeficiency virus (HIV, AIDS virus), it enters the victim’s body cells and utilizes their genetic machinery, their DNA, to reproduce itself. In this process the virus is able to enter the host cell’s chromosomes where it may remain hidden for some time before causing obvious signs of disease, or it may immediately interfere with the normal function of infected cells causing signs of illness shortly after infection. Because FIV prefers T-lymphocytes, a specific type of white blood cell important to the immune system, for replication many of the problems it causes are due to immune system dysfunction.


FIV is a fragile virus that cannot survive outside the infected cat. It dies quickly at room temperature, and it is easily killed by common disinfectants (e.g., household bleach). Therefore, FIV is transmitted only by close contact between cats. The virus is found in the blood, cerebrospinal fluid, and in the greatest quantities in saliva. Since infection is found most often in free-roaming male cats, it is thought that the most common way it is spread is via bite wounds. Mother cats may also transmit the virus to their kittens before they are born, but this is apparently an uncommon event.


Following infection with FIV, there may be no noticeable symptoms of disease, but some cats develop fever, low white blood counts, and/or enlarged lymph nodes about four to six weeks following a bite wound. The lymph node enlargement may last for weeks or even months unaccompanied by any other signs. Infected cats that show no symptoms or that appear to recover from their initial illness can seem healthy for months or even years (the latent phase) during which they can be particularly dangerous to other cats since unaware owners will often let these infective cats go outdoors or mingle indoors with other apparently healthy cats. Eventually, though, most FIV-infected cats develop the chronic stage of illness that is characterized by suppression of the immune system (immunodeficiency), cancer, and/or signs of illness related to almost any organ or organ system.

Cats who are concurrently infected with other viruses such as feline leukemia virus are particularly likely to show early signs of illness and to die soon after infection. FIV infection also makes cats more likely to die from other infections that thrive in an immunodeficient animal (e.g., toxoplasmosis, Haemobartonella infection, yeast infection, calicivirus). The most common problems seen in infected cats are inflammation and infection of the gums and mouth (gingivitis, stomatitis) and nonspecific signs of illness such as weight loss, fever, lack of appetite. Other problems that may signal infection with FIV are enlarged lymph nodes, anemia and other blood count abnormalities, persistent or recurrent signs of upper respiratory disease (sinus infection), conjunctivitis, bronchial inflammation, diarrhea (indicating inflammation of the bowel), skin and ear infections (abscesses, mite infection), urinary bladder dysfunction (cystitis), eye inflammation, neurologic abnormalities, and nervous system damage that can result in seizures and/or bizarre forms of mental deterioration.

Infected female cats may abort or have other reproductive difficulties. This pattern of illness so closely resembles that found in people infected with human immunodeficiency virus (acquired immune deficiency syndrome, AIDS) that the disease caused by FIV is often called feline AIDS. Up to one third of all sick cats may be carrying the feline immunodeficiency virus. Your veterinarian may request a blood test for FIV whenever your cat shows signs that are suspicious of infection and especially in cases of chronic mouth disease. Unfortunately, FIV cannot be confirmed in all cats by a blood test and sometimes false positive tests are found. This is especially true for kittens testing positive under twelve weeks of age. To assure correct results test positive young kittens should be retested after twelve weeks of age.

If your cat does test FIV positive, he or she should be kept indoors and away from other test-negative cats to limit further spread of the disease. Should you consider euthanasia a positive screening test should be confirmed by other blood tests before taking this final step.


Treatment for FIV is directed primarily against secondary infection and toward the organs that are malfunctioning. Antibiotics, fluids, vitamins, and nursing are important aspects of supportive care to insure the longest, most comfortable survival of an affected cat. Antiviral drugs are also sometimes beneficial. Protect your cat against FIV by not allowing him or her to roam unsupervised outdoors where an infected cat may be encountered. It is also important not to admit new cats (especially strays) to your household until they have been quarantined for at least one month and blood tested for FIV.