Understanding FIP Relapse: Why It Happens and What to Do

Key Takeaways

• FIP is treatable: GS-441524 has changed FIP from a fatal disease to one that is manageable, with very high 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 return of the same infection, while reinfection happens when a cat is exposed to a new strain.

• Early detection matters: Loss of appetite, fever, weight loss, or abdominal swelling after treatment can indicate 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 long ago, hearing the words “your cat has FIP” felt like the end of the road. Feline Infectious Peritonitis (FIP) was once considered untreatable, leaving families devastated and without real solutions.

But that has changed. Thanks to groundbreaking research—such as the work of Dr. Niels Pedersen at UC Davis in 2018—GS-441524 injections have completely reshaped the outlook. Recovery rates now exceed 92% when treatment is given for the full 84 days. Cats that once had no chance can now return to their playful, healthy lives.

And yet, even with these advances, relapse does occasionally occur. Around 3% of cats may show symptoms again after finishing treatment. For cat parents in the GCC, it’s important to know: relapse doesn’t mean the fight is over—it simply means your cat may need further care.

What Is FIP Relapse?

Relapse means that after completing treatment—even if your cat looks healthy—small traces of the virus may remain hidden in the body and later become active again. Think of it like weeds in a garden: most are removed, but a stubborn root may grow back if not fully gone.

This is different from reinfection, which occurs when your cat is exposed to a completely new strain of feline coronavirus. According to veterinary studies, including research from UC Davis, relapse typically appears within the first three months after treatment ends.

In simple terms:

• Relapse: The same FIP infection was not fully cleared and has come back.

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

This distinction is important: relapse requires restarting treatment, while reinfection may call for prevention measures, especially in multi-cat households.

Why Does Relapse Happen?

If GS-441524 works so well, why can relapse happen?

Incomplete Viral Suppression

If treatment ends too early, small amounts of the virus can remain in the body. Even tiny traces can regroup and cause symptoms to return. Studies show that completing the full 84-day course (and sometimes longer) greatly reduces this risk.

Drug Resistance

Viruses can adapt under medication pressure. The feline coronavirus may mutate, making it harder to eliminate. In these cases, higher doses of GS-441524 are typically needed to overcome resistance.

Owner Compliance and Dosing Errors

Treating FIP can be overwhelming. Missed doses, underdosing, late administration, or splitting capsules incorrectly can give the virus a chance to survive. Research shows that strict dosing schedules are critical. Using veterinary-prepared GS-441524 formulations helps reduce mistakes.

In addition, stress or other illnesses during the observation period can act as external triggers for relapse.

Early Signs of FIP Relapse

Relapse often begins with subtle signs. After treatment ends, watch carefully for:

• Loss of appetite or refusal to eat

• Weight loss, even with normal food intake

• Recurrent fevers above 39.5 °C (103.1 °F)

• A swollen abdomen or fluid buildup

• Neurological symptoms: unsteady walking, wobbling, or seizures

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

⚠️ If you notice any of these signs, act quickly. Cats are skilled at hiding illness, so once symptoms are visible, urgent veterinary care is required. Early detection gives your cat the best chance for recovery.

Treatment Strategies for Relapse

Here’s the positive news: relapse is not the end. When it happens, the standard treatment is restarting GS-441524 injections—but this time at a higher dose than before.

The goal is to fully suppress the virus, especially in difficult areas like the eyes and nervous system. The length of treatment may vary—anywhere from 2 weeks for mild relapse to up to 12 weeks for severe cases.

We know relapse can be emotionally and financially exhausting for cat owners who have already completed one treatment cycle. That’s why we created the CureFIP™ Relapse Program—to provide guidance, support, and treatment options tailored to cats in the GCC.

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Summary

• FIP is no longer a death sentence—thanks to GS-441524, most cats recover fully.

• Relapse is rare, affecting around 3% of cases.

• Causes of relapse include incomplete suppression, viral resistance, dosing errors, and stress or illness during recovery.

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

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