FIV in Cats: Signs, Testing and Caring for a Positive Cat

What FIV is and how cats catch it

FIV is a retrovirus, in the same broad family as the virus behind HIV in people, but it only infects cats. It lives in an infected cat's saliva and blood and is passed on mainly when one cat bites another deeply enough to break the skin. That is why unneutered males that roam and fight are the cats most often infected. Cornell Feline Health Center puts infection at about 2.5 to 5 percent of healthy cats in North America and 15 percent or more among sick or high-risk cats.

Casual contact rarely spreads it. Sharing food bowls, mutual grooming and sleeping together carry a low risk in a calm household where cats do not fight. An infected mother can occasionally pass the virus to her kittens, most often when she was infected during pregnancy. Once infected, a cat carries FIV for life, but a positive test is not the same as being sick: illness may take years to appear, if it ever does.

Signs of FIV in cats

In the first one to three months after infection, some cats have a mild fever, low energy, poor appetite and swollen lymph nodes, which owners often miss or put down to a passing bug. Then comes a long quiet stage that can last months to years, when the cat looks completely well even though the virus is still present.

As the immune system weakens, the signs are mostly those of infections that will not clear up. VCA Animal Hospitals and Cornell describe red, sore gums and mouth inflammation, weight loss, poor appetite, recurring fevers, eye inflammation, repeated skin, ear, bladder or upper respiratory infections, and ongoing diarrhea. Some cats in the late stage develop cancers, blood disorders, seizures or behavior changes. None of these signs is unique to FIV, which is why a blood test is needed.

When to call your vet today

Call your vet promptly if your cat has been in a fight and has a bite wound or a swelling that could be an abscess, especially if the other cat was a stray or unknown. Book a visit soon for weight loss, a mouth that looks red or seems painful when eating, infections that keep coming back, or a cat that is generally quieter and eating less than usual.

If you already know your cat is FIV-positive, call sooner rather than later for any new sign of illness, even one that would seem minor in another cat. A positive cat's immune system has less in reserve, and VCA and Cornell both stress that secondary infections should be found and treated early. Ask your vet to test any new cat before it joins your household.

When it's an emergency

Go to your vet or the nearest emergency vet straight away if your cat is breathing with effort or with its mouth open, collapses, has a seizure, stops eating and drinking for a day, has pale or yellow gums, or has repeated vomiting or severe diarrhea. These signs need same-day care in any cat, and they can move faster in a cat whose immune system is weakened.

A very high fever, a large hot swelling, or a wound that smells or is leaking pus also needs to be seen quickly. If you are not sure how urgent something is, phone your vet or an emergency clinic, tell them your cat is FIV-positive, and describe what you are seeing so they can advise you on timing.

What you can safely do at home

Do not give your cat any human medicine or leftover pet medicine; many common painkillers are dangerous to cats, and only your vet can decide what an FIV-positive cat should take. What helps most at home is a steady, low-stress routine. Keep your cat indoors so it cannot fight, pick up infections or pass the virus on, and give it its own food and water bowls if it shares a home with other cats.

Cornell and VCA both advise feeding a complete commercial diet and avoiding raw meat, raw eggs and unpasteurized dairy, which can carry germs a weakened immune system struggles with. Keep up with parasite control and dental care, watch your cat's weight and appetite, and keep a simple note of any changes to share at checkups.

What the vet will likely check

The usual first test is a quick in-clinic blood test for antibodies to FIV, often run alongside the feline leukemia test. A positive result is normally confirmed with a second, different laboratory test. Timing matters: antibodies can take up to about eight weeks to appear, so a cat infected recently may test negative and should be retested later. Kittens can test positive for months because of antibodies from their mother, so young kittens are retested as they grow.

For a cat known to be positive, both Cornell and VCA recommend checkups about every six months, with blood and urine tests at least yearly. The vet will check the mouth, lymph nodes, eyes, skin and weight, and treat any secondary infection promptly. Antiviral medicines exist, but they help only some cats and can have side effects, so they are a decision for your vet.

Prevention

Because most infections come from fights, keeping cats indoors and having them spayed or neutered are the two most effective steps. Test every new cat before it meets your others, and keep newcomers separate until the result is back. Cornell notes that no FIV vaccine has been sold in North America since 2016, so prevention here relies on limiting fights rather than on a shot.

A positive diagnosis is not a reason to give up on a cat. Many FIV-positive cats live happy, normal-length lives, particularly those that are not also infected with feline leukemia virus. Ideally a positive cat lives as the only cat or with cats that get along calmly, and your vet can help you weigh the risks if you have several cats.

This page is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your pet.