📄 Article highlights
- FIV (feline AIDS) and FeLV (feline leukemia) are two different viruses that weaken a cat's immune system, but they are not transmissible to humans or dogs.
- FIV is mainly transmitted through deep bite wounds during fights, while FeLV spreads more easily through saliva, mutual grooming, and shared food bowls.
- A positive cat can remain asymptomatic for years: only a blood test performed at the veterinarian's office can determine if a cat is a carrier.
- There is no curative treatment, but regular veterinary monitoring, a secure indoor lifestyle, and good hygiene allow many positive cats to live long, comfortable lives.
- Vaccination against FeLV, screening before any adoption or cohabitation, and spaying/neutering to limit fighting remain the best preventive tools.
FIV and FeLV: two distinct diseases, often confused
When a cat is diagnosed as "positive" during a routine blood test, many owners panic without always knowing exactly what it means. FIV (feline immunodeficiency virus, sometimes called "feline AIDS") and FeLV (feline leukemia virus) are two very distinct retroviruses, which have neither the same mode of transmission, nor the same progression, nor the same prognosis. However, they share one essential point in common: both attack the cat's immune system, making it more vulnerable to other infections, without automatically condemning the animal to a short or unhappy life. Understanding the differences between these two viruses is the first step toward calmly supporting a carrier cat, or effectively protecting one that is not yet infected.
FIV, or feline immunodeficiency virus
FIV belongs to the same family of viruses as human HIV, but it is strictly specific to the feline species: it cannot be transmitted to humans, dogs, or any other species under any circumstances. Once contracted, the virus remains in the body for life and gradually weakens the cat's immune defenses, generally over several years. However, many FIV-positive cats live for many years without apparent symptoms, and some will never develop a serious form of the disease.
FeLV, or feline leukemia virus
FeLV is a different virus, also specific to cats, which infects bone marrow and can cause tumors (notably lymphomas), severe anemia, and progressive immunosuppression. Unlike FIV, FeLV infection progresses through several possible stages: some cats manage to eliminate the virus spontaneously thanks to an effective immune response, others become latent carriers without clinical signs for a long time, and some progress toward an active form, which is generally more serious and has a more limited life expectancy. Overall, FeLV is considered more severe and faster-progressing than FIV.
How are these viruses transmitted between cats?
The transmission route differs significantly between the two viruses, which explains why prevention measures are not exactly the same.
FIV is transmitted mainly through deep bite wounds during fights between cats, with contaminated saliva entering the wound directly. This is why unneutered male cats with access to the outdoors, who are more prone to territorial conflicts, represent the most exposed population. Conversely, calm contact between cats (mutual grooming, sharing food bowls, cuddling) poses a very low risk of transmission. Transmission from mother to kittens is possible but rare.
FeLV, on the other hand, is transmitted much more easily through saliva during close and prolonged contact: mutual grooming, sharing food bowls or litter boxes, superficial bites, and also from mother to kittens during pregnancy or nursing. Multi-cat households where cohabitation is close and long-term are therefore more exposed to this virus than single-pet households.
Which symptoms should alert owners?
Signs suggestive of FIV
An FIV-positive cat can remain asymptomatic for months or even years before the gradual appearance of signs such as unexplained weight loss, unusual fatigue, recurring fever, inflamed gums and chronic mouth sores (gingivostomatitis), swollen lymph nodes, or skin, eye, respiratory, or digestive infections that return regularly and heal poorly. In more advanced stages, neurological disorders may appear, but they remain rare.
Signs suggestive of FeLV
In an FeLV-positive cat in the active phase, one most often observes anemia resulting in pale mucous membranes and severe fatigue, loss of appetite and weight, persistent fever, recurring opportunistic infections, and sometimes the appearance of masses suggestive of lymphoma. As with FIV, a cat in the regressive or latent phase may appear perfectly healthy for a prolonged period, which makes screening all the more important to ensure the infection is not missed.
How is the diagnosis made?
Only a blood test performed by a veterinarian can determine with certainty if a cat is a carrier of FIV or FeLV. The screening test used in clinics (rapid ELISA test) detects FIV antibodies or FeLV antigen, respectively, in a few minutes. A positive result in a kitten under six months of age must, however, be confirmed by a new test in adulthood, because maternal antibodies transmitted by the mother can temporarily distort the result for FIV. Similarly, a first positive FeLV test is often rechecked using a second method (notably PCR) to distinguish an active infection from transient exposure to the virus, which some cats manage to eliminate naturally.
This screening is highly recommended before the adoption of any new cat, before introducing a cat into a household that already has one or more, as well as for any cat showing symptoms suggestive of a weakened immune system.
My cat is positive: how do I support them on a daily basis?
An indoor, secure, and stress-free life
Whether it is FIV or FeLV, the most systematic recommendation from veterinarians is to keep the carrier cat exclusively indoors. This avoids both fights that could transmit the virus to other cats in the neighborhood and exposure to additional infectious or parasitic agents that their weakened immune system would struggle to handle. An enriched environment (scratching posts, hiding spots, cat trees, regular play) remains essential for their balance, as there is no reason for a positive cat to give up a stimulating and comfortable life.
An adapted diet and close veterinary monitoring
Quality food, adapted to the cat's age and state of health, helps support their natural defenses. It is also inadvisable to give meat or raw products that have not been checked to an immunocompromised cat, due to the increased risk of foodborne infections. More frequent veterinary monitoring than usual, generally every six months, allows for the early detection of any secondary infection, dental problem, or blood abnormality, and intervention before the situation worsens. Spaying/neutering is also recommended, both to limit high-risk fighting behavior and to reduce hormonal stress.
Cohabitation with other cats
An FIV-positive cat can generally live with negative cats if the household is calm, the animals are spayed/neutered, and there is no fighting or biting. Many multi-cat households live like this without incident for years. Cohabitation with an FeLV-positive cat requires more caution, as the virus is transmitted more easily through simple proximity: it is possible, but ideally with cats already vaccinated against FeLV, and always after personalized veterinary advice taking into account the household's setup.
Can FIV and FeLV be prevented?
Vaccination, especially useful against FeLV
There is an effective vaccine against FeLV, recommended in particular for cats that have access to the outdoors or live in a multi-cat household where the status of all residents is not known. Vaccination is always done after a preliminary negative test, as vaccinating a cat that is already a carrier is useless. There is, however, no widely available FIV vaccine in France to date; prevention therefore relies essentially on behavioral measures and limiting the risk of bites.
Daily preventive measures
Screening any new cat before introducing them into the home, spaying/neutering cats to reduce territorial fighting behavior, limiting unsupervised outings in areas with high feline density, and avoiding sharing food bowls or litter boxes with a cat of unknown status are all simple measures that significantly reduce the risk of transmission without excessively isolating the cats from one another.
What is the life expectancy of a positive cat?
The prognosis differs significantly between the two viruses. Many FIV-positive cats, when properly monitored, live for ten years or more, with a quality of life close to that of an uninfected cat, especially when the diagnosis is made early and veterinary follow-up is regular. The progression of FeLV is on average faster, with a life expectancy often estimated at between two and five years after diagnosis for active forms, although cats in the regressive phase can remain stable for a very long time. In both cases, the cause of death is not always directly linked to the virus itself, but to the opportunistic infections or complications it promotes: hence the vital importance of attentive veterinary monitoring throughout the animal's life.
In a multi-cat household, giving each cat their own food bowl rather than sharing the same container is a simple measure that limits the exchange of saliva at mealtime, a common-sense action that complements veterinary recommendations.
A diagnosis that should not be viewed as a death sentence
Receiving an FIV or FeLV diagnosis for your cat is always a difficult moment, but it does not mean the end of a happy life. With adapted veterinary monitoring, a secure indoor life, careful nutrition, and plenty of attention, the vast majority of carrier cats continue to enjoy their home, play, ask for cuddles, and live alongside their owners for many years. The most important thing remains establishing a relationship of trust with your veterinarian, who is the only professional capable of adapting monitoring to the specific situation of each cat.
Frequently asked questions
Can FIV or FeLV be transmitted to humans or dogs?
No, these two viruses are strictly specific to the feline species. They pose no risk of transmission to humans, dogs, or any other species in the home.
Can a positive cat live with other negative cats?
It depends on the virus and the context. Cohabitation with an FIV-positive cat is often possible in a calm household without fighting. For FeLV, greater caution is required due to easier transmission; veterinary advice is essential to evaluate each situation.
Should I have all my cats tested if one of them is positive?
Yes, it is highly recommended to test all cats in the household as soon as a case is detected, in order to adapt the care of each one and organize the cohabitation as best as possible.
Is there a treatment that cures FIV or FeLV?
No, there is currently no curative treatment for these two viruses. Management aims to support the immune system, treat secondary infections promptly, and regularly monitor the cat's general state of health.
My kitten tested positive for FIV: is it definitive?
Not necessarily. A kitten born to a carrier mother may have maternal antibodies transmitted temporarily, without being infected themselves. A new test is recommended after the age of six months to confirm or rule out the kitten's true status.
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