Explainer

FIV and FeLV in Cats: What a Positive Test Means

Feline immunodeficiency virus and feline leukaemia virus explained: how they spread, testing, vaccines, and how long cats live with them.

Updated October 2026 · 8 min read · By the Hushku editorial team · 3 sources

Short answer

FIV and FeLV are viruses that weaken a cat's immune system. FIV spreads mainly through deep bite wounds, and many FIV-positive cats live normal lifespans with good care. FeLV spreads through saliva and close contact, is more serious (median survival about 2.5 years after diagnosis), and is preventable with vaccination, which is now core for kittens. Every new cat should be tested.

Key facts

FIV spreads mainly through deep bite wounds; FeLV through saliva and close contact.
Many FIV-positive cats live normal lifespans.
Median survival after an FeLV diagnosis is about 2.5 years.
FeLV vaccination is core for kittens; there's no FIV vaccine in North America.

Definition

Feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV) are retroviruses that infect cats for life and can suppress the immune system. FeLV can also cause cancers and blood disorders.

The two viruses are often tested for together, but they behave very differently.

FIV is found in about 2.5–5% of healthy cats in North America, according to Cornell Feline Health Center, and in 15% or more of sick or high-risk cats. It's spread mainly through bite wounds, so unneutered male cats that fight are most at risk. Casual contact like sharing bowls or grooming is not an efficient route, and mother-to-kitten spread is rare.

FeLV affects about 2–3% of cats in the US and Canada, rising to as high as 30% in ill or high-risk cats. It spreads in saliva, urine, faeces and milk, through grooming, shared bowls and litter boxes, bites, and from mother to kittens. Kittens are far more vulnerable than adults. The virus survives only a few hours outside a cat's body.

Signs and symptoms

Often no signs for months or years
Recurring infections that are slow to clear
Gum and mouth inflammation (gingivostomatitis)
Weight loss and poor appetite
Fever and enlarged lymph nodes
Pale gums from anaemia (especially FeLV)
Cancers such as lymphoma (much more common with FeLV)

Causes and risk factors

FIV: deep bite wounds from an infected cat
FeLV: prolonged close contact, mutual grooming, shared bowls and litter, bites, and mother to kittens
Outdoor access, fighting, and living with infected cats raise the risk

Treatment

There's no cure for either virus
Prompt treatment of secondary infections and other illnesses
Wellness checks at least every 6 months, with blood and urine tests
Good dental care
Antiviral or immune-support treatments in some cases, under your vet's guidance

Prevention

Test every new cat before it meets your other cats
Vaccinate kittens against FeLV (core for kittens) and continue for cats at risk, such as those going outdoors
Neuter cats to reduce roaming and fighting
Keep cats indoors or in a secure outdoor enclosure
There's no FIV vaccine available in North America

What a positive test means

In-clinic tests screen for FIV antibodies and FeLV protein (antigen). Positive results should be confirmed with a second, different test, because false positives happen. Kittens under six months can test FIV-positive from their mother's antibodies without being infected, so they should be retested. For FeLV, a follow-up PCR test and repeat testing after 6 to 12 weeks help tell a progressive infection from a regressive one, where the cat has contained the virus.

Life expectancy

Cornell notes that many FIV-positive cats live normal lifespans if well cared for and not also infected with FeLV. For FeLV, median survival after diagnosis is about 2.5 years, and can be much longer for cats with regressive infections. Cats with FeLV should be kept indoors and away from uninfected cats.

Caring for an FIV or FeLV-positive cat

Keep them indoors, neutered and at a healthy weight; feed a complete diet and avoid raw food, which carries infection risks; and see your vet at the first sign of illness. Cornell advises keeping FIV-positive cats indoors and separate from other cats. Some shelters do place them with calm cats that don't fight, because spread without bite wounds is uncommon, so ask your vet about your household. FeLV spreads more easily, so FeLV-positive cats are best kept as single cats or with other FeLV-positive cats.

Free tools for this

Sources

We check guides against veterinary sources and update them when guidance changes. How we write and review.

Questions.

Can people or dogs catch FIV or FeLV?

No. Both viruses only infect cats.

Should I adopt an FIV-positive cat?

Many FIV-positive cats make wonderful pets and live long, healthy lives. Ask the shelter about the cat's health and temperament, and plan regular vet checks.

Does the FeLV vaccine cause a positive test?

No. FeLV vaccines don't cause false positives on the standard FeLV test.