Feline leukemia virus (FeLV) infects between 2% and 3% of all cats in the United States and Canada. That number has dropped significantly over the past few decades thanks to effective vaccines and routine testing, but FeLV remains one of the most important infectious diseases in cats. How likely your cat is to encounter it depends heavily on lifestyle, age, and where you live.
Overall Prevalence in North America
The 2% to 3% figure represents the general cat population, but it masks wide variation depending on a cat’s living situation. Indoor-only pet cats test positive at a rate of about 1.5%. Cats allowed outdoors have roughly double the risk, testing positive at 3.6%. The difference comes down to exposure: FeLV spreads primarily through saliva, so mutual grooming, shared food bowls, and bite wounds during fights are the main routes of transmission. The virus also shows up in milk, urine, and feces, though saliva carries the heaviest viral load by far.
Sick cats carry much higher rates. Among sick pet cats with outdoor access, about 7.3% test positive for FeLV. Sick feral cats show the highest rates of any group, with roughly 15% testing positive in one large North American study published in the Journal of the American Veterinary Medical Association. Healthy feral cats, interestingly, test positive at only about 1%, likely because cats with persistent infections don’t survive long in feral colonies.
Rates Vary Widely by Country
FeLV prevalence outside North America can be dramatically different. Southern European countries have some of the highest rates: Italy and Portugal each show infection rates around 20% in studies that account for all stages of infection, including cats carrying the virus without obvious symptoms. Germany and France have much lower rates, closer to 9% in the same research. A separate pan-European survey of over 6,000 cats across 30 countries found the highest rates in Portugal (8.8%), Hungary (5.9%), Italy (5.7%), and Malta (5.7%), while Germany came in at just 0.3% and France at 1.0%.
The gap between southern and western Europe likely reflects differences in vaccination rates, the size of free-roaming cat populations, and how aggressively testing programs have been adopted. In well-managed catteries that use test-and-removal protocols, FeLV has been essentially eliminated.
Why the Numbers Have Dropped
FeLV was far more common before widespread vaccination and testing became standard veterinary practice. Over the past 25 years, prevalence in North America has fallen substantially. Routine screening at shelters and veterinary clinics means infected cats are identified early, which limits spread. Vaccination provides strong protection for cats at risk of exposure, particularly those living in multi-cat households or spending time outdoors.
That said, the decline appears to be leveling off. Recent European data suggests the downward trend in prevalence has stagnated, which likely reflects the difficulty of reaching unvaccinated outdoor and feral populations. Cats that never visit a vet are the ones most likely to carry and spread the virus undetected.
Kittens Face Higher Risk Than Adults
Young cats are considerably more vulnerable to FeLV than adults. A kitten’s immune system is less equipped to fight off the virus during initial exposure, which makes early vaccination especially important. Adult cats with mature immune systems are more likely to mount a successful defense against the virus and clear it before it becomes a permanent infection.
Not Every Positive Cat Stays Infected
One of the most important things to understand about FeLV is that a positive test doesn’t always mean a lifelong infection. The virus follows different paths depending on how a cat’s immune system responds.
In a progressive infection, the immune system fails to contain the virus. The cat remains persistently infected, sheds large quantities of virus in saliva and nasal secretions, and poses a significant transmission risk to other cats. These cats typically develop serious health problems over time, including cancers, blood disorders, and immune suppression that leaves them vulnerable to secondary infections.
In a regressive infection, the cat’s immune system stops viral replication before or shortly after the virus reaches the bone marrow. These cats don’t have active virus circulating in their blood and aren’t shedding it to other cats, though traces of viral DNA remain embedded in their cells. One Brazilian study found that among FeLV-positive cats, about 34% had progressive infections while roughly 10% had regressive infections. The remaining cats fell somewhere in between or had cleared the virus almost entirely.
This distinction matters because a cat with a regressive infection can live a normal, healthy life. Retesting a few weeks after an initial positive result helps clarify which path the infection is taking.
How Testing Works
Most veterinary clinics use a rapid blood test that detects a specific viral protein. These screening tests are highly accurate, with specificity rates at or near 100% in studies, meaning false positives are rare. A saliva-based version of the test exists and shows sensitivity around 93% to 100%, though its specificity is somewhat lower (around 85% to 92%), so a positive saliva test typically needs confirmation with a blood test.
If a screening test comes back positive, your vet will usually recommend a confirmatory test using a different method. This second test looks for the virus inside white blood cells and helps determine whether the infection is progressive or regressive. Testing is recommended for all new cats before they enter a household, especially if other cats are already living there.
Multi-Cat Households and Shelters
Sharing a home with an FeLV-positive cat does increase risk for other cats in the household. The virus spreads most efficiently through prolonged close contact: grooming each other, eating from the same bowls, and using the same litter boxes. Sharing litter pans with an infected cat increases the environmental viral load, since the virus can be shed in feces, though this is a secondary transmission route compared to saliva.
FeLV doesn’t survive long outside a cat’s body. It’s fragile and easily killed by disinfectants, drying, and sunlight. Casual or brief contact between cats is unlikely to transmit the virus. The highest-risk scenario is a household where cats groom each other regularly or where an infected cat has free access to communal food and water sources over weeks or months.