FIV (Feline Immunodeficiency Virus, or Feline AIDS)

FIV (Feline Immunodeficiency Virus, or Feline AIDS)

Animals Affected



FIV is a virus that is related to HIV, the human AIDS virus.  Experts do not believe FIV is capable of infecting humans.  FIV causes a syndrome in cats that is similar to human AIDS.

Most FIV-infected cats catch the virus by fighting with other cats.  The virus spreads when an infected cat bites a cat that is not infected.  A much smaller number of cats catch the virus from their mother as kittens.  Sexual transmission of FIV does not appear to be common.

FIV suppresses the immune system of infected cats.  This causes increased vulnerability to infections with bacteria, fungi, and parasites.

Cats suffer severe side effects from or do not respond well to the types of therapies that successfully suppress the development of AIDS in HIV-infected people.  Therefore, the treatments for FIV are very limited.

Despite the lack of treatments for FIV, many cats never develop complications from the virus.  These cats lead basically normal lives.

The cats that develop health problems as a consequence of FIV generally develop the problems 7 – 10 years after infection with the virus.   Because 7 years is a large portion of a cat’s normal life expectancy, premature death is far from universal in FIV-positive cats.


Many FIV-infected cats show no symptoms whatsoever.   However, if the virus causes significant suppression of the immune system the following symptoms are possible.

  • Frequent, recurrent, or persistent infections are a frequent symptom of FIV infection. Infections of the respiratory system, urinary system, skin, ears or other systems may not respond to appropriate treatment, or they may recur after the treatment is stopped.
  • FIV-infected cats may exhibit weight loss, diarrhea, lack of appetite, lethargy, or an unkempt coat.
  • Rarely, FIV infection triggers behavior changes such as aggression or house soiling.

Risk Factors and Prevention

Most cats catch FIV by fighting with other cats.  The virus spreads when an infected cat bites an uninfected cat hard enough to break the skin.  FIV is not spread by casual contact such as grooming or sharing food, water, litter, or bedding.  Because of this, it is not common for FIV to spread among cats that live in the same household.

  • Because most cat fights occur outdoors, access to outdoor areas is the main risk factor for infection with FIV.  Cats that are kept in stable indoor environments have an extremely low chance of contracting the virus.  Prohibiting access to outdoor areas is the most effective way to prevent FIV infection in cats.
  • Males suffer higher rates of FIV infection than females.
  • Cats that are more than six years old are more likely to be FIV-positive.
  • Cats who fight regularly are at high risk of FIV infection.  Cats in this group often have a history other complications from fighting, such as abscesses, lacerations (cuts), and scratches on the skin.
  • Kittens born to FIV-infected mothers may catch the virus during nursing.

A vaccine for FIV exists.  However, it is not commonly used.  Many experts doubt that the vaccine effectively prevents infection with FIV.  The vaccine may cause uninfected cats to test positive for the virus.


  • Some FIV-infected cats never suffer complications from the virus.
  • Increased susceptibility to disease and infections is the leading complication.
  • FIV-infected cats are capable of spreading the disease to other cats during fights.
  • Stomatitis, a severe inflammation of the mouth and gums, is sometimes a consequence of FIV infection.
  • Severe suppression of the immune system may lead to death.


Simple blood tests can check for the presence of FIV antibodies in the body.  These tests may falsely give a negative result during the first four to six weeks of infection with FIV.

Experts recommend verifying positive test results by running a second, more advanced test for antibodies to the virus.

If a kitten is born to an FIV-infected mother but does not catch the virus, the kitten may falsely test positive for FIV for up to 14 weeks.  Because of this, kittens that test positive for FIV when they are less than 14 weeks old should be re-tested after they are older than 14 weeks.


Treatments such as AZT and combination antiviral therapy (which are effective in preventing the development of human AIDS) are not commonly used in cats.

FIV treatment focuses on early and aggressive treatment of infections and other medical problems that develop due to the cat’s weakened immune system.  Owners of FIV-infected cats should seek veterinary attention at the first sign of illness in their pet so that the problem can be addressed while it is most treatable.


Experts recommend that FIV-infected cats not be allowed outside.  Outdoor cats suffer increased rates of abscesses and other bacterial and fungal infections.  FIV-infected cats also may spread the virus to other cats while they are outside.

Raw meats may be contaminated with bacteria or parasites that can sicken cats with FIV. FIV-infected cats should not be allowed to hunt, and their diets should not contain raw meat.

Fleas spread a number of feline diseases. FIV-infected cats are highly susceptible to these diseases. All FIV-positive cats should receive effective flea prevention.

Prednisone and other drugs designed to modify the response of the immune system must be used cautiously in FIV-infected cats.


FIV does not frequently spread among cats that live in the same household.  Cats that cohabitate rarely engage in the aggressive, severe form of fighting that spreads the virus.

FIV does not appear to have the ability to affect humans.  However, FIV-infected cats may be highly susceptible to pathogens such as ringworm, Salmonella, Campylobacter, and E. coli that pose a risk to people.  Owners of FIV-infected cats should be aware of this, and should seek veterinary attention at the first sign of illness in their pet.

Copyright © Eric Barchas, DVM.   All rights reserved.
The contents of this page are provided for general informational purposes only. Under no circumstances should this page be substituted for professional consultation with a veterinarian.