Understanding FIP Relapse: Why It Happens and What to Do

Key Takeaways

• FIP is treatable: GS-441524 has turned FIP from a fatal disease into a manageable one, with excellent recovery rates when given correctly.

• Relapse is rare: Only about 3% of cats may experience a relapse after completing treatment.

• Relapse vs reinfection: Relapse means the same infection returns, while reinfection happens when a cat encounters a new strain.

• Early detection matters: Loss of appetite, fever, weight loss, or abdominal swelling after treatment can be signs of relapse.

• GS-441524 is the best option: Relapse cases require restarting GS-441524 injections, often at higher doses.

• Veterinary supervision is essential: Only licensed veterinarians can confirm relapse and adjust treatment safely.

Not too long ago, hearing “your cat has FIP” was devastating news. Feline Infectious Peritonitis (FIP) was once considered a death sentence for cats, leaving families across Australia and New Zealand with no real hope.

But today, things look very different. Thanks to groundbreaking research—such as the work of Dr. Niels Pedersen at UC Davis in 2018—GS-441524 injections have transformed the outlook. Recovery rates now exceed 92% when treatment runs for the full 84 days. Cats that once had no chance now return to their playful, happy selves.

Even so, relapse can sometimes occur. Around 3% of cats may show symptoms again after treatment finishes. If you’re a cat parent in Oceania, remember: relapse does not mean the battle is lost—it simply means your cat may need additional treatment.

What Is FIP Relapse?

Relapse happens when, after completing treatment—even if your cat appears healthy—hidden traces of the virus become active again. Think of it like weeds in the garden: most are removed, but a stubborn root can grow back if not completely cleared.

This is not the same as reinfection, which occurs when your cat encounters a completely new strain of feline coronavirus. According to veterinary studies, including UC Davis research, relapse usually appears within the first three months after treatment ends.

Here’s the difference in simple terms:

• Relapse: The same FIP infection wasn’t fully cleared and has come back.

• Reinfection: Your cat encounters a new strain of the virus from the outside environment.

This distinction matters because relapse requires restarting treatment, while reinfection may call for prevention strategies—especially in multi-cat households.

Why Does Relapse Happen?

If GS-441524 is so effective, why does relapse occur?

Incomplete Viral Suppression

If treatment is cut short, tiny amounts of the virus can remain in the body. These remnants may later regroup and cause symptoms to return. Studies show that completing the full 84-day protocol (and sometimes extending it) greatly lowers this risk.

Drug Resistance

Viruses are constantly evolving. Under medication pressure, feline coronavirus can mutate, making it harder to eliminate. In such cases, higher doses of GS-441524 are usually required to overcome resistance.

Owner Compliance and Dosing Errors

Treating FIP is demanding. Missed doses, underdosing, late injections, or incorrect splitting of capsules can give the virus space to survive. Research confirms that precise, consistent dosing is critical. Veterinary-prepared GS-441524 formulations reduce the risk of errors.

External stressors or concurrent illness during the observation phase can also act as triggers for relapse.

Early Signs of FIP Relapse

Relapse usually begins subtly. After treatment, keep an eye out for:

• Loss of appetite or refusal to eat

• Weight loss, even with normal food intake

• Recurrent fevers above 39.5 °C

• A swollen belly or fluid accumulation

• Neurological signs: unsteady walking, wobbling, or seizures

• Eye changes: cloudiness, inflammation, lethargy, or unusual glow

⚠️ If you notice these signs, act quickly. Cats are skilled at hiding illness, so once symptoms become visible, urgent veterinary care is essential. Early action offers the best chance for recovery.

Treatment Strategies for Relapse

The good news is that relapse does not mean the end. The standard approach is to restart GS-441524 injections—this time at a higher dose than before.

The goal is to fully suppress the virus, including in difficult areas like the eyes and nervous system. Treatment duration can vary, from 2 weeks in mild relapses to up to 12 weeks in severe cases.

We understand relapse can feel overwhelming, especially for cat parents in Oceania who have already been through the treatment journey once. That’s why we created the CureFIP™ Relapse Program—to provide guidance, support, and tailored treatment options for your cat.

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Summary

• FIP is no longer fatal—thanks to GS-441524, most cats now recover fully.

• Relapse is rare, affecting around 3% of treated cats.

• Relapse happens due to incomplete suppression, viral resistance, dosing mistakes, or external stressors.

• Watch for appetite loss, weight loss, fever, swollen abdomen, neurological signs, or eye changes.

• The best relapse treatment is restarting GS-441524 injections at higher doses, with close veterinary supervision.