What are FIV, FeLV, and FIP?

FIV, FeLV, and FIP are three of the most well known feline viruses, but there are many common misunderstandings and incorrect assumptions made about them.

First: FIV and FeLV are NOT death sentences for your cat!

FIV – Feline Immunodeficiency Virus

Of the three viruses, FIV is the one that is least contagious and least lethal. It is the one most similar to human AIDS and the primary concern is that is suppresses the cat’s immune system, so any health issues are actually due to secondary infections. So being proactive any time your cat shows any signs of illness will go a long way toward them having a long and happy life.

The most common route of infection is a deep bite wound from an FIV-positive cat to another cat. It can also be transmitted via blood, in utero and from the milk of an infected mother cat. It is very rare for cats to get FIV just from being around infected cats, sharing food bowls, or from a person touching an FIV-positive cat and then touching an FIV-negative cat. Many FIV-positive cats and FIV-negative cats live together in the same home for years without spreading the virus to the non-infected cats.


The vast majority of cats will be much less aggressive after they have been spayed or neutered (especially neutered males as they are no longer driven by testosterone). Many vets still treat FIV as an absolutely deadly disease, which can cause a lot of unnecessary fear in pet owners, because FIV is NOT a death sentence! If one of your cats is diagnosed with FIV and they have been living peacefully with your other cats, there is no reason why they cannot continue to do so for many years to come.

FeLV – Feline Leukemia Virus

FeLV is passed from one cat to another through saliva, blood, and to some extent, urine and feces. The virus does not live long outside the cat’s body, usually no more than 15 minutes after it has left the host’s body. FeLV positive cats and FeLV negative cats should not be housed together, but they can be kept in the same facility/building while easily preventing the spread of infection between cats.

Exposure to infected cats raises your cat’s risk of contracting FeLV, especially for kittens and young adult cats. Older cats are less likely to contract the infection, because resistance seems to increase with age. For indoor-only cats, the risk of contracting FeLV is very low. Cats in multi-cat households or in catteries are more at risk, especially if they share water, food dishes, or litter boxes.

Like FIV, FeLV is NOT a death sentence, but it can be more fatal long term than FIV with 80% of cats passing within 3 years of diagnosis with FeLV. Only about 3% of cats in single-cat households have the virus, but for cats that spend time outdoors, the rate is much higher. Still, the prevalence of FeLV has decreased over the last 25 years because of vaccines and increased knowledge of the virus.

FIP – Feline Infectious Peritonitis

While the other two viruses mentioned have much happier outcomes, historically FIP is much more deadly. Almost all indoor and outdoor cats already have the coronavirus, which is a harmless but extremely contagious virus in cats. FIP is the result of the coronavirus mutating in to a deadly virus with two forms, a wet (effusive) and dry (non-effusive). The mutation is rare and while most cats have the coronavirus only a very small percentage will ever suffer from FIP. The virus also seems more likely to mutate when the cat is under severe stress (environmental changes, surgeries, or severe illness for example).

FIP is fatal is 100% of untreated cats, which is a tough statistic to hear considering how widespread the coronavirus is, but luckily the mutation is very rare and there are treatments under development for FIP and the non-mutated coronavirus that will hopefully become widely available in the next few years. As of the time of this article, there is no FDA approved treatment for FIP and a cat cannot be “cured” of the coronavirus.

While the current outcome is bleak, there are treatments for FIP that are awaiting FDA approval, including a cure for the coronavirus that completely blocks the virus from replicating and infecting new cells, essentially isolating the virus until it is eliminated entirely by the natural replacement of cells over time. You can find more information on the potential cure here.

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