All Cats Need Love -In Health and in Sickness

May 7, 2025

8 min read

Updated: Aug 22, 2025

Living with FIV/FeLV is possible.

In the past, the recommended treatment for a cat diagnosed with FIV or FeLV was euthanasia. Today, we know that these viruses are not an immediate death sentence for a cat. But, they can live happy and healthy lives after being diagnosed. It’s very uncommon for cats with either illness to require euthanasia immediately following their diagnosis. We’ll get into why today.

So, what is FIV?

Feline immunodeficiency virus or FIV is a disease that only affects cats, so humans and other animal species will never contract it. It’s similar to HIV in humans in that it attacks and weakens the immune system, it can lead to feline AIDS and there is no known cure.

This means an infected cat will have a more difficult time fighting off secondary infections. Many times these secondary infections become long-term or permanent for the cat.

FIV is relatively uncommon, infecting around 2.5–5% of cats in North America. This could be due to the virus being too weak to survive outside a cat’s body for more than a few hours. It’s primarily shed through saliva, but blood contact and sexual transmission is possible as well. The most common mode of transmission is through bite wounds from territorial fights, thanks to those mating hormones -mostly.

A pregnant cat can pass FIV onto her kittens through her womb, milk or bite wounds. This is another reason why it’s so important to get community cats spayed.

Stages.

There are three stages of FIV infection: acute, asymptomatic and progressive immunocompromised. But, not every cat will experience all three. Many cats stay in the asymptomatic phase for the rest of their lives.

FIV is often overlooked by owners as they don’t notice any odd behavior with their cats for months or years -it can be invisible for a long time.

The acute phase is the beginning of FIV, taking hold around 1–3 months after infection. During this phase, the virus travels to the lymph nodes and reproduces in white blood cells that are known as T-lymphocytes. It then spreads to other lymph nodes throughout the body and causes temporary enlargement. This can bring on fever, lack of appetite, and depression.

During the asymptomatic phase, the virus replicates very slowly inside the cells of the immune system, lasting for months to years. Some cats may show abnormalities in their blood work, like low white blood cells or increased proteins.

This tends to happen when bodies are fighting off an infection. This stage is generally functionable, so they can live an average lifespan as a healthy, happy cat.

In further years the virus can move into the progressive immunocompromised phase, where secondary infections can occur. Infections of the skin, eyes, urinary, tract, or upper respiratory tract. It’s common for infected cats to develop severe gum and dental diseases and significantly more likely to develop cancer and blood disorders.

It’s a hard truth, but keep in mind that when a cat contracts multiple infections like this, their survival time can be just a few months.

Not every case is as severe as the next, but it’s important to keep a close eye on every FIV infected cat.

Diagnosis.

Around 2–6 months following infection, the cat's immune system will start to produce the antibodies it needs to fight the infection and it will continue to do so for their lifespan.

When testing for FIV, blood samples are examined to find traces of these antibodies -and usually multiple tests are done because one isn't reliable enough. Very rarely a cat in the later stages can develop immune systems so compromised that they don't produce enough antibodies to be detectable.

Vaccines for FIV were discontinued in 2016 because its presence causes the cat to produce antibodies that are very difficult to distinguish from ones naturally produced.

Treatment and Management.

Although a cat infected with FIV can live a very happy and healthy life, it's impossible to predict their lifespan. Since there's no known cure, the most important thing you can do for an infected cat is reduce/eliminate their exposure to other cats, especially if they're sick or start showing signs of such. Keep the cat indoors as this will eliminate any exposure to diseases they might encounter on the street.

And, obviously, this will eliminate the spread to other cats they meet.

Like any other cat, they should be fed a balanced, nutritional diet. Raw meats, eggs, and unpasteurized dairy products should never be fed to a FIV infected cat as their immune systems aren't equipped to deal with any food-borne bacteria.

Deep dive into more information on FIV here.

What about FeLV?

Feline Leukemia Virus (FeLV) has some similarities to FIV, but they are not the same disease -a cat can have either one or both. It is not contractible to any other animal species or humans and around 2–3% of cats in North America are infected with FeLV.

Studies have shown that 80–90% of FeLV-infected cats will die within three to four years of initial diagnosis.

FeLV causes a variety of diseases as well as leukemia. It enters the cells inside the cat's immune system and blood-forming tissues (bone marrow/lymphatic tissues) which leads to the death or genetic mutation of the cell.

This results in weakened white blood cells, leaving the cat more vulnerable to infections than a healthy cat. White blood cells attack infections, so when they're weakened, the infection has an easier time taking hold to control the cellular environment.

While these changes can potentially make the cells cancerous, it can take months or years to take effect -if it does at all. The most common tumor to develop is a lymphoma but other diseases are more of a threat.

Many FeLV infected cats will develop moderate to severe immune system suppression making it more difficult to fight off minor infections. Intestinal inflammation, neurological and ocular diseases are common as well.

Stages.

Within the three stages of FeLV, the virus continues to spread throughout the body while the cat's immune system readily fights it. In the abortive infection phase, the virus replicates on the cat's tonsils as they show little to no signs of illness.

Approximately 20–30% of cats successfully fight off the virus before it progresses further.

When a cat fails to fight off the initial infection, it finds the bone marrow and compromises the immune system. After this, it can take 2–3 years for the cat to develop further issues such as anemia, skin diseases and leukemia. This is called progressive infection. Cats in this stage are significantly contagious, so they should never be housed with uninfected cats or be allowed outside.

Around 30–40% of cats will enter the progressive infection phase.

Another possibility is regressive infection where the cat has been persistently infected to the point that their immune system develops an effective response to the virus. They will still carry the virus within their genome, but they enter a low risk phase of the virus.

This means FeLV related diseases will not come as easily to them as they did before, though this phase tends to be temporary. It's very unlikely that a cat in regressive infection will spread the virus to other cats other than through a blood transfusion.

An estimated 30–40% of cats enter the regressive phase, making reliable testing even more difficult to achieve.

Diagnosis.

Depending on what stage the cat is in, it can be a tricky situation when assigning a diagnosis. When a cat is in abortive infection, they should be thoroughly tested 8–12 weeks after the first positive test.

Progressive infection is fairly easy to diagnose since the virus is so active and spread out. A rapid blood test can be performed that detects the viral antigens present in the cat's body. These tests are very reliable but there's always a degree of uncertainty, so false positives and negatives rarely occur.

Treatment and Management.

When dealing with FeLV, it's important to treat any secondary infections as they occur because that's what's really going to harm the cat.

Unfortunately, there is no cure available for FeLV, so most infected cats will die or require euthanasia as they get too sick to live a quality life. There are currently vaccines available, so if your cat ever goes outside, talk to their veterinarian to see if a FeLV vaccine is ideal.

Cats receiving a FeLV vaccination should always be tested prior as it will put needless strain on an infected cat's immune system -more isn't always better. Kittens are highly susceptible to infection and disease so it's recommended that all kittens be vaccinated.

Always remember that vaccines are not 100% effective, so they could still contract the virus if they're exposed to it.

Read this article for even more information on FeLV.

The other side to testing.

Alley Cat Allies has been advocating for community cats for over three decades and they have a different take on testing for FIV and FeLV in strays. Community cats are strays that have been "adopted" by the community, meaning they have feeding stations and living quarters in an outdoor area.

ACA believes testing should not be done when acquiring community cats as it often results in immediate euthanasia.

Because some cats can fight off FeLV in the early stages, a cat on its path to immunity, may be euthanized before they see that day. Infection rates for FIV and FeLV are relatively low while testing is not as accurate as it should be. It normally takes multiple tests making it financially impractical with limited funding and labor to manage testing and housing.

Prioritizing viral testing over sterilizing strays would be a poor decision on behalf of the community. Besides TNR being the only effective plan to eliminate strays while avoiding euthanisia, FIV and FeLV would likely see a decrease in transmission naturally as TNR is carried out. This is because many bites within the community are a result of mating practices as well as instinctual sexual aggression.

And obviously, sterilized females will not pass it onto kittens.

I didn't think about it this way until I read ACA's article, and I totally see their point. It wouldn't make much sense to test cats for viral infections when the growing stray population poses a more dangerous threat. Funds and labor should be allocated to consider the bigger picture. If we focus on viral testing rather than reducing the stray population, we may never see the day where stray animals are a scarcity.

Read ACA's blog to get their reasoning for yourself.

Can infected cats live with uninfected cats?

This question can be tricky because it really depends on how cautious you are. FIV is primarily transmitted through biting, so if the house is peaceful, you could make it work.

Cats with FeLV can live with uninfected cats and cats with FIV as long as all FeLV-negative cats are vaccinated and there are no fights or rough play. You have to remember vaccines are not 100% effective, so this poses a high risk.

Housing infected cats with uninfected cats can be possible, but cats are very unpredictable, so just because they've never had an incident in the past doesn't mean it can't happen in the future. In my non-veterinary opinion, you should play it safe and keep cats isolated.

Another option you may not have thought about is checking in with local shelters. Some shelters have the ability to house cats with FIV and FeLV, so this could be a more comfortable option for you and your cat.

Moving forward.

If you take anything away from this, it should be that almost every cat with FIV or FeLV can live a happy, functional life. Animals should only be euthanized in extreme cases and this most certainly does not classify as such.