That range is not a universal estimate for all cat populations or a current figure for every country. Prevalence depends on the region, cats studied and test used. Exposure risk is therefore assessed according to the cat's contacts and the local situation.
When to see a vet urgently
Contact a vet immediately if a cat with confirmed or suspected FeLV infection develops severe symptoms:
- very pale mucous membranes and marked weakness;
- laboured or noticeably rapid breathing at rest;
- not eating and deteriorating general condition;
- collapse or inability to move normally.
Overview
FeLV is a retrovirus, meaning that after infection it integrates its own genetic material into the cat's cells. This leads to chronic disease: the virus can remain dormant for a long time and reactivate later, causing serious damage. Unlike many other infections, cats cannot fully “recover” from FeLV: they either remain permanent carriers or eventually die from complications.
That description of permanent carrier status does not apply to every exposed cat. In an abortive infection, the immune system stops the virus before it permanently integrates into the cells' genetic material. In a regressive infection, viral genetic material remains in the body, but ongoing replication is suppressed. In a progressive infection, the virus replicates continuously and the risk of illness is substantially higher. Prognosis therefore cannot be inferred from exposure alone.
Routes of transmission
The main routes of transmission are:
- Direct contact through saliva, mutual grooming and bites
- Shared food bowls, toys and litter trays
- From mother to kittens during pregnancy or nursing
- Blood contact through bites or transfusions
FeLV is unstable in the environment and is rapidly inactivated, so it most often spreads through prolonged direct contact with infected cats.
Shared items do not present the same risk as close saliva contact: transmission through a litter tray is less common than through mutual grooming or saliva-contaminated bowls, for example. Progressively infected cats are the most important sources of infection. A cat in the regressive phase does not usually shed the virus, but is unsuitable as a blood donor because transmission through transfusion is possible.
FeLV and FIV are different viruses. Both can affect immune defences, but their transmission routes, tests and disease courses are not the same. Infection status is therefore investigated separately for each virus when testing is indicated.
How the disease develops and progresses
Once inside the body, the virus enters lymphoid tissue and bone marrow. Infection develops in stages:
- Primary viraemia: the virus circulates in the blood and initial symptoms may appear
- Secondary viraemia: the virus becomes established in the bone marrow and infection becomes chronic
- Progressive form: serious complications, including anaemia, tumours and immunodeficiency
- Latent form: the virus remains in cells, possibly without symptoms, but can reactivate with stress or weakened immunity
This list is not a sequence that every cat goes through. In a regressive infection, viral antigen may no longer be detectable in the blood, although integrated provirus, the virus's DNA, remains in the body. Reactivation is possible, but does not occur in every cat. Some of these cats live for a long time without FeLV-related disease.
The word leukaemia can also be misleading: a positive FeLV result does not mean the cat already has leukaemia or another cancer. The virus can disrupt bone marrow cell production without a tumour. In anaemia, there are too few red blood cells to carry oxygen, which can cause pallor, weakness and rapid breathing. A blood count helps assess how blood cell production is functioning.
Symptoms of FeLV in cats
Symptoms vary with the stage of disease:
- Tiredness, listlessness and reduced appetite
- Weight loss and a poor coat
- Recurrent, severe infections because of immunodeficiency
- Anaemia, with pale mucous membranes, weakness and rapid breathing
- Enlarged lymph nodes
- Cancers, including lymphoma and leukaemia
- Reproductive problems, including miscarriages and infertility
- Stomatitis, gingivitis and chronic inflammation
Some cats may have no symptoms for a long time, but sudden deterioration in health remains possible.
Complications and consequences
FeLV is dangerous because of its many consequences:
- Immunodeficiency: the body cannot fight off even mild infections
- Cancers, particularly lymphoma and leukaemia
- Severe anaemia and disrupted blood cell production
- Chronic inflammation, including stomatitis, rhinitis and skin inflammation
- Premature death, with a substantially shorter lifespan in infected cats
The generalisation about shortened lifespan applies mainly to progressive infection. The prognosis for regressive infection can be considerably better. Even a progressively infected cat can remain free of symptoms for a long time. A positive test alone is not a reason for euthanasia: decisions depend on diagnosed disease, condition and quality of life.
Veterinary diagnosis
FeLV is detected using the following methods:
- Rapid ELISA tests to detect viral antigens in blood
- IFA to detect viral proteins
- PCR to detect viral DNA
- Repeat tests a few weeks apart in uncertain cases
- Further investigations, including a complete blood count, ultrasound and X-rays if a tumour is suspected
One screening result is generally not enough to determine the final infection type. A positive result is confirmed using another method or a repeat sample according to the vet's plan. False-positive results are also possible. A negative test performed very soon after exposure does not reliably rule out infection, so the timing of exposure is part of the history.
The rapid ELISA test looks for FeLV p27 antigen, a structural viral protein, rather than antibodies produced by the cat. PCR can identify provirus integrated into the cells' genetic material. An antigen test can therefore be negative while PCR is positive without the results being incompatible: this combination can fit a regressive infection. Results are assessed alongside changes over time and the cat's other circumstances.
Vaccination does not itself make an FeLV antigen test positive. If a previously vaccinated cat tests positive, the result should therefore not automatically be explained by the vaccine. As well as diagnosing infection, the cause of any anaemia, inflammation or tumour is investigated. Not every problem in an FeLV-positive cat is directly caused by the virus.
Treatment and everyday monitoring
There is currently no reliable treatment that eliminates the virus from the body in progressive or regressive FeLV infection. Antiviral medicines and products affecting the immune system have been studied, but evidence of long-term clinical benefit is insufficient. They should not be regarded as a certain cure. Treatment focuses on the cat's identified problems and maintaining a good quality of life.
A bacterial infection, for example, is treated with appropriate medication, severe anaemia may require a blood transfusion, and cancer treatment may be considered for a tumour. Options are assessed individually. Tiredness or weight loss should therefore not simply be accepted as an inevitable consequence of FeLV without investigation: a treatable problem may be present.
At home, monitor appetite, weight, activity, toileting and changes in the mouth and eyes. Record slower eating, weight loss or changes in behaviour. A new symptom is a reason to contact the vet early. Follow-up is tailored individually, with particular attention to oral health, lymph nodes and changes in the blood count.
Provide nutritionally complete cat food. Avoid raw meat and unpasteurised dairy products because they can increase the risk of bacterial and parasitic infections. Body fat and muscle condition are assessed alongside weight. Living indoors reduces new exposures and the spread of infection, but the cat still needs appropriate opportunities for play, rest and other daily activities. An uncrowded, calm environment also makes monitoring easier.
Prevention
Complete protection against FeLV is not available, but risk can be reduced through:
- Vaccination, recommended for kittens and cats at risk
- Keeping cats indoors and limiting contact with outdoor cats
- Testing new cats before they live together
- Regular veterinary checks
- Good nutrition and reduced stress to support immune defences
The FeLV vaccine helps prevent infection-related risks, but does not remove an infection already present. Cats are tested before a vaccination decision, and the need is assessed according to age, contacts and local disease patterns. Even placing a vaccinated cat in ongoing close contact with an infectious cat is not risk-free.
In a household with several cats, their infection status is established and the safety of living together is planned with the vet. Restricting contacts may be necessary while testing is under way. Washing bowls alone does not replace preventing direct contact between infectious and unprotected cats. Cleaning and ordinary good hygiene complement the overall plan.
What it means for owners
FeLV is a chronic disease that significantly affects a cat's quality and length of life. Owners should remember:
- The virus does not infect people or other animal species
- Infected cats need special care
- Vaccination remains an important means of protection
- Early diagnosis helps manage disease progression
The statement about other species refers here particularly to people and animals such as dogs. However, FeLV can infect some other members of the cat family besides domestic cats. In everyday pet care, the main focus of prevention is contact between cats.
The vaccination plan distinguishes FeLV vaccination from other vaccinations. Prevention of other major infectious diseases is not automatically stopped in an already infected cat; the suitability of vaccinations is assessed according to health and risk. Oral care and appropriate parasite control are also part of an individual health plan.
This text is for information only and does not replace veterinary treatment. If your cat develops symptoms, seek veterinary attention.
Frequently asked questions
Can an FeLV-positive cat have a good life?
Yes. The form of infection and any associated diseases affect the prognosis. Some cats remain well for a long time. Treatment and monitoring aim to identify treatable problems and preserve quality of life.
Does a positive rapid test definitely mean permanent infection?
Not on its own. The result is confirmed, and repeat investigations can monitor the course of infection. Antigen tests and PCR measure different things, so their combination helps distinguish forms of infection. The vet interprets results alongside exposure information.
Can the FeLV vaccine cure an already infected cat?
No. The vaccine is used for prevention and does not remove an existing infection. Care for an infected cat targets its condition, diagnosed diseases and prevention of other infections.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
- GUIDELINE for Feline Leukaemia Virus Infection, European Advisory Board on Cat Diseases, accessed 2026-11-03.
- Feline Leukaemia Virus, Cornell University, accessed 2026-11-03.
- Feline Leukaemia Virus Disease, Merck Veterinary Manual, accessed 2026-11-03.
- 2020 AAFP Feline Retrovirus Testing and Management Guidelines, American Association of Feline Practitioners, accessed 2026-11-03.
- 2024 guidelines for the vaccination of dogs and cats, WSAVA, accessed 2026-11-03.
- Feline leukaemia virus (FeLV) infection in domestic pet cats in Australia and New Zealand: Guidelines for diagnosis, prevention and management, Australian Veterinary Journal, accessed 2026-11-03.