Home » Pet Health » Feline Infections and Viruses » Signs and Symptoms of an FIV Infection?


Feline immunodeficiency virus (FIV) is a retrovirus, which means it uses the host cells to multiply. The reproduction of the virus can take some time. As a result, your FIV-positive cat may initially appear healthy after infection. How the disease progresses and presents itself in your cat depends on the following three phases:

    1. Acute phase: The acute phase occurs 1 to 3 months after the initial infection. The virus starts infection when it enters the immune cells and begins to replicate. The virus then travels throughout the body. During this time, there is an initial activation of the cat’s immune system as it tries to fight off the virus. During this time, the cat may experience a loss of appetite, fever, depression, and enlarged lymph nodes. However, the signs are so subtle that pet owners miss the symptoms in this stage.
    1. Asymptomatic phase: The cat then enters the asymptomatic phase that can last from months to years. During this stage, the virus replicates in immune cells called B and T lymphocytes and continues to spread in the body. The cats may show some blood work abnormalities during their vet checkups during this time, but they won’t otherwise show any outward symptoms of illness. Many FIV-infected cats stay in this stage for years and never progress to the next phase.
    1. Feline Acquired Immunodeficiency Syndrome (AIDS): If the disease continues to progress, the cat will develop feline AIDS, a stage of severely weakened immunity where they are most likely to develop secondary infections or illnesses. The most common symptom of this stage includes oral diseases, including inflammation of the gums and mouth ulcers or sores.

What are the symptoms of FIV infection?

FIV infection gradually impairs the immune system, making cats susceptible to other conditions and diseases. Contrary to healthy cats that resolve the infection on their own or with treatment, FIV-infected cats exhibit recurrent infections or illnesses that worsen progressively over time. Also, the illnesses might not respond well to treatment. While the symptoms may change based on the life cycle of the virus, overall, the most common symptoms of FIV infection include:

    • Persistent fever
    • Recurrent illness
    • Low white blood cell count
    • Swollen lymph nodes
    • Fatigue
    • Weight loss
    • Intestinal inflammation
    • Inflammation of mouth and lips
    • Swollen and blistered skin
    • Inflammation or redness around the eyes

The initial symptoms may not be evident when your cat becomes infected with FIV. Therefore, keep an eye out for subtle changes, especially if your pet has been around an FIV-positive cat. As the disease progresses, the symptoms become more apparent. However, the signs, like those above, may be due to many possible causes. Therefore, it is essential to consult your vet to determine if your cat has an FIV infection. Once you receive a diagnosis, you and your vet can discuss how to care for your cat.

The Pet Cancer Foundation’s Website Editorial team is comprised of veterinarians, veterinary oncologists, and veterinary technicians, as well as scientific writers and editors who have attained their PhD’s in the life sciences, along with general editors and research assistants. All content found in this section goes through an extensive process with multiple review stages, to ensure this extended resource provides pet families with the most up-to-date information publicly available.

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Last Updated: October 13, 2022


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The following sources were referenced to write the content on this page:

Eckstrand, CD, Sparger, EE & Murphy, BG 2017, ‘Central and peripheral reservoirs of feline immunodeficiency virus in cats: a review’, J Gen Virol, vol. 98, no. 8, pp.1985-1996.

Elder, JH, Sundstrom, M, de Rozieres, S, de Parseval, A, Grant, CK & Lin, Y-C 2008, ‘Molecular mechanisms of FIV infection’, Vet Immunol Immunopathol, vol. 123, no. 1-2, pp. 3-13.

Hartmann, K 2012, ‘Clinical aspects of feline retroviruses: a review’, Viruses, vol. 4, no. 11, pp. 2684-2710.

Hosie, MJ & Lutz, H 2022, Schalm’s Veterinary Hematology, 7 edn., Wiley Online.

Ravi, M, Wobeser, GA, Taylor, SM & Jackson, ML 2010, ‘Naturally acquired feline immunodeficiency virus (FIV) infection in cats from western Canada: prevalence, disease associations, and survival analysis’, Can Vet J, vol. 51, no. 3, pp. 271-276.

The Pet Cancer Foundation’s medical resource for pet owners is protected by copyright.

For reprint requests, please see our Content Usage Policy.