Most cats carry feline enteric coronavirus at some point. It lives quietly in the intestines and does nothing. In a small number of cats it mutates, becomes pathogenic, and sets off an inflammatory response the body cannot switch off. That is FIP.

FIP is treatable. FIP is curable. Cats in India have been cured and are asleep on someone's bed as you read this. If your cat was diagnosed today, you have not run out of time. You have run out of good information — and that is what this page is for.

The virus you're thinking of is not the virus you have

Feline enteric coronavirus (FCoV) is common, usually harmless, and lives in the gut. It passes between cats in litter trays. Most infected cats show nothing, or a brief bout of diarrhoea.

FIP is what a small fraction of those infections become when the virus mutates inside the individual cat. Your cat did not "catch FIP." FIP is not passed cat to cat — the mutation happens in the body it happens in.

This matters practically, not just academically: a FCoV antibody titre tells you very little on its own. Half the cats in a shelter would test positive. Cats under two are most frequently affected — but no cat is too old for FIP.

Myth: "the test says coronavirus positive, so it's FIP." No. A FCoV titre is not a FIP diagnostic, and never was.

The five forms

These aren't five diseases

They're five places the inflammation went. A cat can move between them — which is why a diagnosis from three weeks ago is not a diagnosis today.

Wet (effusive)

High temperature, appetite gone, lethargy. Abdomen filling with fluid — visibly enlarged, rounded, bloated. Sometimes vomiting, diarrhoea, jaundice. Moves fast.

Pleural

The same lethargy, fever and appetite loss — but the fluid is in the chest. Laboured breathing. Frequently misread as pneumonia — and that mistake costs days a cat may not have.

Dry (non-effusive)

No fluid. Chronic, slower — weeks to months. Fatigue, gradual weight loss, then organ-specific signs: liver, mesenteric lymph nodes, kidney, pancreas, spleen, gut. Hardest to diagnose.

Ocular

The virus reaches the eyes. Cloudy eyes, dilated or uneven pupils, a change in the colour of the iris. Inflammation or bleeding in the anterior chamber.

Neurological

The virus crosses the blood-brain barrier. Uncoordinated movement, head tilt, unsteady walk, incontinence, seizures, paralysis, personality change. In these cases, bloodwork can look completely normal.

Combinations are common

A cat can have more than one form at once, and treatment is dosed by the most serious one present. Repeat examination is not optional — the cat you assess in week three is not the cat you assessed in week one.

What FIP looks like, day to day

A fever antibiotics won't touch. This is the one that gets missed — a cat cycled through antibiotics with a fever that keeps returning is a cat nobody has diagnosed.
Weight going down with nothing else to explain it.
A belly getting rounder while the cat gets thinner.
Lethargy that isn't a mood — a cat that has stopped being a cat.
Laboured or fast breathing. That is today's problem, not tomorrow's.
Sudden clumsiness in a young cat — wobbling, falling, a head that tilts.
An eye that has changed colour or gone cloudy.

A clean blood panel does not clear a cat

In ocular and neurological FIP, bloodwork can be completely normal. Diagnosis then rests on clinical signs, imaging, and response to treatment — not on one reassuring report.

How FIP is diagnosed — and how it gets misdiagnosed in India

The honest sentence first: there is no single confirmatory blood test for FIP. A diagnosis is built — from signalment, history, clinical signs, bloodwork patterns, fluid analysis, imaging, PCR on the right sample, and often the response to treatment itself.

What builds the case: bloodwork patterns (lymphopenia, raised globulins, an albumin-to-globulin ratio below 0.5, raised bilirubin, raised acute-phase proteins); fluid analysis where there's an effusion (protein-rich, total protein above 3.5 g/dL); and ultrasound, where mesenteric lymphadenopathy is one of the earliest and most telling findings.

PCR is a real tool. The sample decides whether it tells the truth.

On the correct sample, PCR is one of the most dependable confirmatory tools available. A positive on effusion, or on a fine-needle aspirate of a mesenteric lymph node, is highly specific for FIP.

The right sample, by form: wet/pleural → effusion; dry → mesenteric lymph node aspirate; ocular → aqueous humor; neurological → cerebrospinal fluid.

Now the part nobody selling you a drug will tell you: in India, PCR is routinely run on blood. Blood PCR is unreliable. It produces false positives and false negatives, and it is a leading source of FIP misdiagnosis in this country. If a lab has given you a blood PCR result and called it a diagnosis — that is not a diagnosis.

India can prove a cat has FIP. It can't prove a cat doesn't.

A positive PCR on the right sample confirms it. A negative confirms nothing — especially in dry FIP, where there may be no effusion to test at all.

Immunohistochemistry (IHC) is the test that closes that gap — the gold-standard confirmatory test. It is not available anywhere in India: not at a private lab, not at a teaching hospital, not for any price. Which means a cat here can be proven to have FIP, but never cleared of it — and that asymmetry is where the misdiagnoses live, including the cruellest kind: the cat sent home because a test came back clean.

FSGI Foundation is working with a diagnostic laboratory to change that. It is one of the reasons this organisation exists.

Differentials — what else looks exactly like this: lymphoma, pyothorax, chylothorax, cardiac effusion, toxoplasmosis, hypoalbuminaemia. A vet who hasn't ruled these out hasn't diagnosed FIP.

Is FIP curable?

Yes. In 2016, Dr. Niels Pedersen's team at UC Davis achieved the first successful FIP treatments. In 2019, the same group's field trial of GS-441524 changed the disease permanently. Since then, hundreds of thousands of cats worldwide have been treated and cured.

Not managed. Not in remission. Cured — a defined endpoint: a minimum 84-day treatment course, followed by 84 days of observation with no antivirals. If nothing abnormal appears in that window, the cat is considered cured. That's 168 days. Anyone selling you thirty is selling you a calendar, not a cure.

The catch, stated plainly: these drugs are not approved for veterinary or human use in India — confirmed in writing by CDSCO in reply to RTI Ref. CDSCO/R/E/25/00266, dated 29 July 2025. That vacuum is exactly where an unregulated market grew, and why what gets sold to frightened families needs watching.

Myth: the dose stays the same as the cat gains weight. It must not. A dose that isn't raised as a recovering cat grows is a dose that shrinks every week — and underdosing is the leading cause of relapse. Weigh weekly, round up, never down.

What actually kills cats now

The virus is no longer the main thing killing cats with FIP in India. These are: misdiagnosis (a blood PCR, a titre, a shrug — weeks gone); underdosing (the most common cause of relapse); stopping early (the cat looks well on day 40; the cat is not well on day 40); and being sold a story — a confident cure timeline, a success rate with no study under it, a combination product with no feline safety data.

We are a nonprofit. We don't sell medicine, we take no money from anyone who does, and we are not affiliated with any manufacturer or supplier. That isn't a disclaimer. It's the reason this page can tell you the truth.

What is FIP?