Feline Immunodeficiency Virus (FIV)

Published on
Last updated on
8 min read

Key takeaways

Feline immunodeficiency virus (FIV) is an uncommon viral disease of cats, caused by a retrovirus similar to human immunodeficiency virus.

  • FIV destroys white blood cells and disrupts the immune system. As a result of this immunosuppression, cats with FIV are predisposed to severe, repeated, or long-lasting infections and to developing cancers
  • FIV is spread when infected cats bite other cats. Cats that are prone to fighting, such as intact males with outdoor access, are at highest risk of FIV infection
  • Symptoms of FIV are typically mild and include lethargy, fever and enlarged lymph nodes
  • FIV is diagnosed using a blood test. In some situations, retesting is needed to confirm the cat’s FIV status.
  • There is no treatment for FIV, but appropriate management reduces the impact of the disease
  • Prevention of FIV in uninfected cats involves keeping them indoors, spaying or neutering to reduce fighting behavior, and testing new cats for FIV before introduction into the home
Are you concerned?

Connect with a vet to get more information about your pet’s health.

Book an online vet

A closer look: Feline Immunodeficiency Virus (FIV)

There are three stages of FIV infection: the acute phase, latent phase, and progressive phase.

The acute phase occurs first, within 1-3 months after the infecting bite wound. The virus spreads to lymph nodes where it affects the immune system and produces mild symptoms such as lethargy, lack of appetite, and swollen lymph nodes.

The latent phase starts once the acute stage has resolved. This phase has no symptoms. This phase lasts anywhere from months to years. The virus continues to infect white blood cells and destroy them at a very slow rate, but the immune system compensates to prevent most infections.

The progressive phase begins when the immune system is no longer able to compensate for the damage to the white blood cells. This is characterized by repeated or long-lasting infections of the skin, eyes, urinary tract, upper respiratory tract, and gums. Cats are also more likely to develop cancer and other immune system dysfunctions than healthy cats once the disease has progressed this far.

The severity of the progressive stage depends on the number of infections the cat has, whether tumors are present, and their overall health before entering the progressive stage. Cats with multiple severe infections or multiple tumors have a poor prognosis.

Connect with a vet to get more information

With DVM, ICH certifications and great reviews by pet parents like you for this symptom

Risk factors

Feline immunodeficiency virus is uncommon, particularly in indoor cats. It affects approximately 2.5-5% of all cats in North America.

Cats at particular risk for FIV infection are intact males with outdoor access, but any cat interacting with others is potentially at risk.

Transmission between cats in stable social relationships with no fighting is extremely uncommon, but still occurs.

FIV is a life-long condition that has no definitive treatment. FIV-positive cats require intensive management, such as routine wellness exams and blood work, and must be monitored closely for signs of infection. They often require changes to their lifestyle to prevent them from spreading the virus to other cats.

Many cats live normal, healthy lives despite an FIV diagnosis. Cats in the asymptomatic (latent) stage of infection have a similar lifespan to non-infected cats, and some cats remain asymptomatic for their entire lives. Cats with late stage, progressive disease have a poor prognosis, particularly if they have multiple infections or tumors.

Possible causes

Feline immunodeficiency virus is caused by a retrovirus, a similar virus to human immunodeficiency virus. FIV only infects cats.

FIV is primarily spread through cat bites. The virus is shed in infected cats’ saliva, allowing it to be transferred to a bitten, uninfected cat.

Main symptoms

The early stages of FIV infection often have mild or no symptoms.

Symptoms during late stage infection are due to immunosuppression caused by damage to the white blood cells. Symptoms seen during this phase are typically the result of secondary infections.

More advanced FIV-positive cats show a variety of symptoms depending what type of infection(s) they acquire.

Testing and diagnosis

FIV is diagnosed using a simple blood test. In some cases, a second test may be recommended. There are some situations where false negatives and false positives can occur. If circumstances warrant, multiple retests may be ordered to confirm positive or negative results.

It is recommended that FIV-positive cats have wellness exams every six months to monitor them for signs of infection and disease progression.

Steps to Recovery

There is no treatment for FIV. However, many cats have normal, healthy lives after being diagnosed. Management of FIV for healthy cats focuses on reducing their risk of infections. Strategies to accomplish this include:

  • Moving the cat to an indoor-only lifestyle
  • Eliminating raw meat, raw eggs, and unpasteurized dairy products from the cat’s diet
  • Using year-round antiparasitic medications to prevent parasitic infections
  • Keeping them up-to-date on their routine vaccinations to prevent other infectious diseases.

Owners must closely monitor their FIV-positive cats, as even the smallest infections have the potential to become serious. Cats living with FIV may need antibiotics as a precaution for routine medical procedures.

There are some antiviral treatments under investigation for use in FIV-positive cats. The efficacy of these treatments is still being assessed.

FIV is incurable. Despite the virus’ effects on the immune system, approximately 64% of FIV-positive cats live long lives with only periodic illness. Once FIV is in the progressive phase, life expectancy declines.


IV is contagious to other cats. It cannot spread to people. FIV testing is recommended prior to bringing home any new cat or kitten.

FIV-positive cats who have non-aggressive social relationships with other cats are not expected to transmit the disease to their housemates, but there will always be some risk of transmission. Even if a FIV-positive cat never bites a non-infected cat, it is important that owners understand having an FIV-positive cat poses some risks to other cats in the household.

Strategies to prevent the spread of FIV in multi-cat households include:

  • Segregating infected cats away from non-infected cats
  • Not introducing new cats into the home
  • Ensuring all cats are up-to-date on vaccinations, to prevent the infected cat from being exposed to other diseases.

FIV positive cats should also be prevented from spreading the disease to cats outside of their own household. Strategies to reduce transmission include having the cat fixed and moving to an indoor-only lifestyle.

There is a FIV vaccine available in some countries, such as Australia, New Zealand, and Japan. This vaccine is not available in North America.

Due to their reduced immune system function, FIV-positive cats are more likely to develop infections and disease. These infectious agents are shed into the environment and infect other cats. All cats in the household should be monitored closely for signs of illness. Previous homes of FIV-positive cats require thorough cleaning before introducing a new cat or kitten into the home, to remove any infectious agents.

Is Feline Immunodeficiency Virus (FIV) common?

FIV is estimated to affect between 2.5-5% of all cats in North America.

Typical Treatment

  • Symptom management
  • Treatment of recurring infections
  • Environmental management to reduce exposure to pathogens and protect other pets


No Author - Writing for Cornell University College of Veterinary Medicine
Wendy Brooks - Writing for Veterinary Partner
No Author - Writing for American Association of Feline Practitioners

Our editorial committee

Our medical review team is responsible for validating and maintaining the quality of our medical information.