# FIP in cats: causes, signs and diagnosis

> FIP is a serious disease caused by a mutated feline coronavirus. Learn the signs of wet and dry FIP, why diagnosis needs a vet, and how to lower the risk.

Source: https://panduanhewan.org/en/pet-health/fip-in-cats/ · Updated 25 September 2026 · English · Bahasa Indonesia: https://panduanhewan.org/id/kesehatan-hewan/fip-kucing/
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**Review status:** Compiled from the listed veterinary and health organisations’ guidance; not yet reviewed by a veterinarian.

**Caution:** General information for owners, not a substitute for examination, diagnosis or treatment by a veterinarian. If your animal seems very unwell, in pain, struggling to breathe or may have been poisoned, contact a vet immediately.

## Key points

- FIP is caused by feline coronavirus mutating inside a cat's body; the virus is not the Covid-19 virus and does not spread to people.
- Feline coronavirus is very common and spreads mainly through faeces, but only a small proportion of infected cats go on to develop FIP.
- Around 80% of FIP cases are in cats under two years old, especially cats from places with many cats.
- No single test can confirm FIP; vets combine a physical examination, blood tests, imaging and fluid samples.
- FIP used to be almost always fatal, but antiviral treatment under veterinary supervision can now cure most cats.

## When should you see a vet?

- See a vet immediately if your cat is struggling to breathe or breathing fast, has a swollen belly, has seizures, is wobbly on its feet or has yellow gums.
- A fever that comes and goes, lethargy and poor appetite, especially in a young cat.
- Weight loss, or repeated diarrhoea and vomiting.
- Eye changes: cloudiness, redness, blood in the eye, or squinting and avoiding bright light.
- Your cat seems 'not itself', with good days and bad days that come and go.

## What is FIP in cats?

FIP (feline infectious peritonitis) is a serious disease that develops when feline coronavirus mutates inside a cat's body and the cat's immune system reacts in a particular way. The Cornell Feline Health Center explains that most feline coronavirus strains live in the gut and usually cause no significant disease, or only mild diarrhoea. In some cats, the virus changes so that it can infect white blood cells and spread through the body, triggering intense inflammation around blood vessels. PDSA and International Cat Care (ICC) stress that feline coronavirus is not the Covid-19 virus and cannot spread to people. An article from Universitas Airlangga likewise describes FIP as a mutation of feline enteric coronavirus (FECV) into FIP virus (FIPV).

Evidence: [Cornell Feline Health Center — Feline Infectious Peritonitis](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/feline-infectious-peritonitis) · [PDSA — Feline infectious peritonitis (FIP) in cats](https://www.pdsa.org.uk/pet-help-and-advice/pet-health-hub/conditions/feline-infectious-peritonitis-in-cats) · [International Cat Care — Feline infectious peritonitis (FIP)](https://icatcare.org/articles/feline-infectious-peritonitis-fip) · [Universitas Airlangga — Tinjauan tentang Feline Infectious Peritonitis (FIP)](https://unair.ac.id/tinjauan-tentang-feline-infectious-peritonitis-fip/)

## Is FIP contagious to other cats?

Feline coronavirus spreads easily between cats, mainly through faeces in shared litter trays, but FIP itself is not believed to be directly contagious. Cornell explains that FIP develops in individual cats after the virus mutates, and the FIP form is not thought to be shed in faeces, though research continues. PDSA says the virus can also spread via food bowls and mutual grooming. Cornell estimates that 5–10% of exposed cats go on to develop FIP, sometimes weeks to years later. ICC notes that around 80% of cases are in cats under two years old. Pedigree cats, recently stressed cats (for example after adoption or a move) and cats from crowded shelters or catteries are also at higher risk.

Evidence: [Cornell Feline Health Center — Feline Infectious Peritonitis](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/feline-infectious-peritonitis) · [PDSA — Feline infectious peritonitis (FIP) in cats](https://www.pdsa.org.uk/pet-help-and-advice/pet-health-hub/conditions/feline-infectious-peritonitis-in-cats) · [International Cat Care — Feline infectious peritonitis (FIP)](https://icatcare.org/articles/feline-infectious-peritonitis-fip)

## What are the signs of wet and dry FIP?

Early signs of FIP are vague, such as a fever that comes and goes, lethargy, poor appetite and weight loss; a wet, dry or mixed form then develops. PDSA explains that signs may appear suddenly or come and go, with good days and bad days. In wet (effusive) FIP, fluid builds up in the belly or chest, so the belly swells and the cat may struggle to breathe. Cornell notes that the wet form usually progresses relatively quickly. ICC explains that many cats have both forms at different times, so it is important to watch for changing signs.

In dry (non-effusive) FIP, inflammation affects organs such as the kidneys, liver, eyes and brain. According to PDSA and Universitas Airlangga, signs include yellow gums, cloudy or bloody eyes, wobbliness, tremors, seizures, behaviour changes or blindness. A case report from Madiun, East Java, published in ARSHI Veterinary Letters (IPB), describes a cat with dry FIP that stopped eating, was lethargic and jaundiced, and lost a lot of weight. Because many other illnesses cause these signs too, only a vet can judge whether FIP is a likely cause.

Evidence: [PDSA — Feline infectious peritonitis (FIP) in cats](https://www.pdsa.org.uk/pet-help-and-advice/pet-health-hub/conditions/feline-infectious-peritonitis-in-cats) · [Cornell Feline Health Center — Feline Infectious Peritonitis](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/feline-infectious-peritonitis) · [International Cat Care — Feline infectious peritonitis (FIP)](https://icatcare.org/articles/feline-infectious-peritonitis-fip) · [Universitas Airlangga — Tinjauan tentang Feline Infectious Peritonitis (FIP)](https://unair.ac.id/tinjauan-tentang-feline-infectious-peritonitis-fip/) · [ARSHI Veterinary Letters (Sekolah Kedokteran Hewan dan Biomedis IPB) — Peneguhan diagnosa feline infectious peritonitis pada kucing](https://journal.ipb.ac.id/index.php/arshivetlett/article/view/40823)

## How do vets diagnose FIP?

No single test can confirm FIP on its own; a vet reaches the diagnosis by combining several examinations. Cornell explains that a positive coronavirus antibody test only means the cat has been exposed to coronavirus, not that it has FIP. ICC likewise stresses that a positive coronavirus test is not the same as having the disease. Vets usually combine the history, a physical examination, blood tests, an eye examination, X-rays or ultrasound, and tests on fluid taken from the belly or chest. Tests such as PCR can detect the virus's genetic material, but Cornell notes that no test is 100% accurate. In the ARSHI Veterinary Letters case, vets in Madiun confirmed it using blood tests, blood biochemistry and PCR.

Evidence: [Cornell Feline Health Center — Feline Infectious Peritonitis](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/feline-infectious-peritonitis) · [International Cat Care — Feline infectious peritonitis (FIP)](https://icatcare.org/articles/feline-infectious-peritonitis-fip) · [PDSA — Feline infectious peritonitis (FIP) in cats](https://www.pdsa.org.uk/pet-help-and-advice/pet-health-hub/conditions/feline-infectious-peritonitis-in-cats) · [ARSHI Veterinary Letters (Sekolah Kedokteran Hewan dan Biomedis IPB) — Peneguhan diagnosa feline infectious peritonitis pada kucing](https://journal.ipb.ac.id/index.php/arshivetlett/article/view/40823) · [Universitas Airlangga — Tinjauan tentang Feline Infectious Peritonitis (FIP)](https://unair.ac.id/tinjauan-tentang-feline-infectious-peritonitis-fip/)

## Can FIP be cured?

Yes, many cats can now recover: FIP used to be almost always fatal, but research in recent years shows that antiviral treatment cures most cats. ICC says studies show antivirals can cure more than 85% of cats with FIP. Without treatment, PDSA says most cats die within days or weeks of diagnosis. Treatment lasts several weeks and needs regular check-ups, and relapse after treatment ends is possible but uncommon. An article from Universitas Airlangga also notes that antivirals have improved survival, including in cats with neurological signs.

Legal availability of FIP antivirals differs from country to country. ICC explains that a vet must be confident a cat has FIP before starting treatment, because using antivirals in cats that do not have FIP could lead to viral resistance. PDSA warns that black-market medicines are not regulated, so their contents and safety are unknown, and advises getting all medicines through a vet so that dosing and monitoring are correct. For these reasons, do not buy or give FIP medicines yourself. Discuss treatment options, costs and monitoring with your vet.

Evidence: [International Cat Care — Feline infectious peritonitis (FIP)](https://icatcare.org/articles/feline-infectious-peritonitis-fip) · [PDSA — Feline infectious peritonitis (FIP) in cats](https://www.pdsa.org.uk/pet-help-and-advice/pet-health-hub/conditions/feline-infectious-peritonitis-in-cats) · [Cornell Feline Health Center — Feline Infectious Peritonitis](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/feline-infectious-peritonitis) · [Universitas Airlangga — Tinjauan tentang Feline Infectious Peritonitis (FIP)](https://unair.ac.id/tinjauan-tentang-feline-infectious-peritonitis-fip/)

## How can you lower the risk of FIP?

There is no sure way to prevent FIP, but you can lower the risk with clean litter trays, small groups of cats and a low-stress home. ICC and PDSA recommend at least one litter tray per cat plus one extra, cleaned daily and kept away from food and water bowls. Avoid crowding: PDSA suggests ideally no more than four cats in a household, and Cornell recommends no more than three cats per room. An FIP vaccine is available only in some countries; Cornell says its effectiveness is questionable and it is not routinely recommended. PDSA advises keeping a cat with suspected or confirmed FIP apart from other cats, with its own bowls and litter tray.

Evidence: [International Cat Care — Feline infectious peritonitis (FIP)](https://icatcare.org/articles/feline-infectious-peritonitis-fip) · [PDSA — Feline infectious peritonitis (FIP) in cats](https://www.pdsa.org.uk/pet-help-and-advice/pet-health-hub/conditions/feline-infectious-peritonitis-in-cats) · [Cornell Feline Health Center — Feline Infectious Peritonitis](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/feline-infectious-peritonitis)

## Sources & references

1. [Cornell Feline Health Center — Feline Infectious Peritonitis](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/feline-infectious-peritonitis)
2. [PDSA — Feline infectious peritonitis (FIP) in cats](https://www.pdsa.org.uk/pet-help-and-advice/pet-health-hub/conditions/feline-infectious-peritonitis-in-cats)
3. [International Cat Care — Feline infectious peritonitis (FIP)](https://icatcare.org/articles/feline-infectious-peritonitis-fip)
4. [Universitas Airlangga — Tinjauan tentang Feline Infectious Peritonitis (FIP)](https://unair.ac.id/tinjauan-tentang-feline-infectious-peritonitis-fip/)
5. [ARSHI Veterinary Letters (Sekolah Kedokteran Hewan dan Biomedis IPB) — Peneguhan diagnosa feline infectious peritonitis pada kucing](https://journal.ipb.ac.id/index.php/arshivetlett/article/view/40823)

## Keep exploring

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Cite: PanduanHewan. (2026). FIP in cats: causes, signs and diagnosis. PanduanHewan.org. https://panduanhewan.org/en/pet-health/fip-in-cats/