Feline immunodeficiency virus (FIV) infects roughly 1 in 10 cats worldwide. A 2024 systematic review covering studies from multiple continents found an overall seroprevalence of 9.43%, though rates vary significantly depending on where a cat lives, whether it roams outdoors, and whether it’s male or female.
Global and Regional Prevalence
FIV exists on every continent where domestic cats live, but infection rates are far from uniform. Asia has the highest regional prevalence at about 14.3%, followed by Europe at roughly 9%. North America has the lowest documented rate at around 5.9%. These figures come from a meta-analysis pooling data across dozens of studies, so they reflect broad averages. Within any given country or city, local rates can be much higher or lower depending on the density of free-roaming cats and how much fighting occurs among them.
The North American figure may seem reassuringly low, but it still means that in a colony of 20 stray cats, at least one is likely carrying the virus. In shelters, where cats often arrive as strays with unknown histories, the proportion of FIV-positive animals can run higher than the regional average.
Which Cats Are Most at Risk
Male cats are dramatically more likely to test positive for FIV. In one study of free-roaming cats in Florida, males were nearly five times as likely to be infected as females. This isn’t because of a biological vulnerability. It’s behavioral: unneutered male cats fight more, and fighting is the primary way FIV spreads. Intact males roaming outdoors, defending territory, and competing for mates accumulate bite wounds over time, and each bite from an infected cat is an opportunity for transmission.
Outdoor access is the single biggest lifestyle risk factor. Indoor-only cats in stable, non-aggressive households face almost no realistic chance of contracting FIV. The virus doesn’t survive long outside a host, and it requires direct inoculation through a deep bite wound to reliably infect a new cat. Geographic location also matters. Even within the same state, prevalence can vary widely between counties, likely reflecting differences in stray cat populations and management efforts.
How FIV Spreads
FIV passes almost exclusively through bite wounds. Saliva from an infected cat carries the virus, and a deep puncture pushes it directly into the bloodstream or tissue of the bitten cat. This is what makes it so closely tied to fighting behavior.
Casual contact is not an efficient route of transmission. Cats that share water bowls, groom each other, or sleep in the same bed do not appear to pass the virus between them at any meaningful rate. This is a crucial point for anyone who owns or is considering adopting an FIV-positive cat: in a peaceful multi-cat household where cats get along, the risk to other cats is very low. Sexual contact is also not a significant transmission route.
Mother-to-kitten transmission is possible but rare. On uncommon occasions, an infected mother cat can pass FIV to her kittens, and the risk goes up if she becomes newly infected during pregnancy. But this remains an infrequent pathway compared to bite wounds.
FIV and FeLV Co-infection
Some cats carry both FIV and feline leukemia virus (FeLV), though this combination is uncommon. In a large Portuguese study spanning four and a half years, about 1.8% of the total cat population tested positive for both viruses simultaneously. Co-infection matters because each virus weakens the immune system through different mechanisms, and carrying both can accelerate health decline. However, the low co-infection rate means most FIV-positive cats are not also dealing with FeLV.
What Happens After Infection
FIV progresses through distinct phases, and the timeline is often surprisingly slow. After initial infection, a cat may show mild, short-lived symptoms like a brief fever or swollen lymph nodes. This acute phase passes quickly, and the cat then enters a prolonged period where it appears completely healthy. This asymptomatic phase can last years, sometimes the better part of a decade.
During this long quiet period, the virus is slowly weakening the immune system, much like HIV does in humans (the viruses are in the same family). Eventually, some cats progress to a stage where their compromised immunity leaves them vulnerable to secondary infections: chronic mouth inflammation, respiratory infections, skin conditions, and digestive problems. Not every FIV-positive cat reaches this stage. Many live well into old age with proper care, especially if kept indoors where they’re less exposed to infectious agents their weakened immune system would struggle to fight off.
The practical takeaway is that an FIV diagnosis is not a death sentence. Cats diagnosed with FIV can live for many years with a good quality of life, particularly when they receive regular veterinary checkups to catch secondary infections early and stay in a low-stress indoor environment. The virus progresses slowly enough that many FIV-positive cats ultimately die of causes unrelated to the infection.
What This Means for Cat Owners
If you’re adopting a cat from a shelter, there’s roughly a 1-in-10 chance globally (closer to 1-in-17 in North America) that the cat carries FIV. Most shelters test for the virus before adoption, so you’ll typically know the cat’s status upfront. If you already have cats at home and are considering bringing in an FIV-positive cat, the key question is whether your existing cats are aggressive. In a household where cats coexist peacefully without fighting, transmission risk is minimal.
For cats that go outdoors, the calculus changes. Outdoor males face the highest risk, and keeping cats indoors is the most effective prevention. There is no widely available vaccine currently in use in most countries, so avoiding exposure through bite wounds remains the primary strategy. If your cat does go outside and gets into fights, testing for FIV is worth doing, particularly since infected cats can appear perfectly healthy for years while carrying and potentially spreading the virus.