Blog | Paw Promise

What is FIP?

Feline Infectious Peritonitis (FIP) is a serious viral disease caused by a mutated form of the feline coronavirus (FCoV). While most cats that encounter coronaviruses never develop FIP, in some cases the virus mutates inside the cat's body and triggers this life-threatening condition.

FIP can affect cats of any age, but it is most commonly seen in young cats under three years old and in cats living in multi-cat environments like shelters.

Types of FIP

FIP comes in two main forms:

Wet (Effusive) FIP — Fluid accumulates in the abdomen or chest, causing a swollen belly or difficulty breathing.
Dry (Non-Effusive) FIP — Causes inflammation in organs like the eyes, brain, kidneys, or liver, with less obvious symptoms.

Some cats can have a combination of both forms.

Signs to Watch For

Symptoms of FIP can vary depending on the form but often include:

Persistent fever that doesn't respond to antibiotics
Loss of appetite and rapid weight loss
Lethargy and weakness
Swollen abdomen (in wet FIP)
Neurological signs such as wobbling or seizures
Eye inflammation or cloudiness
Jaundice (yellowing of skin or eyes)

If your cat shows any of these signs, please visit a vet as soon as possible.

The Good News: FIP is No Longer a Death Sentence

For many years, FIP was considered almost always fatal. That has now changed dramatically.

A groundbreaking antiviral drug called GS-441524 has shown remarkable success in treating FIP. As of 2024, an oral formulation of GS-441524 is now officially available in the United States, and research continues to expand access worldwide.

With proper treatment:

Many cats achieve full remission
Treatment typically lasts 12 weeks (with research exploring shorter 42-day protocols)
Survival rates have improved enormously compared to just a few years ago

What To Do If You Suspect FIP

See a vet immediately — Early diagnosis improves outcomes.
Ask about GS-441524 — This antiviral is the current gold standard for FIP treatment.
Join a support community — There are wonderful online communities of cat owners who have gone through FIP treatment and can offer guidance and support.
Don't give up hope — Many cats who were given days to live are now living full, happy lives after treatment.

FIP in Shelter Cats

At Paw Promise, we care deeply about every cat in our care. Shelter environments can sometimes increase FIP risk due to stress and close contact between cats. We take proactive steps to reduce stress, provide proper nutrition, and move cats into foster and adoptive homes as quickly as possible — all of which significantly lower FIP risk.

If you have any questions about the health of a cat you are considering adopting, please don't hesitate to reach out to us.

Together, we can make sure every cat gets the care and love they deserve. 🐾