What Are the Early Symptoms of FIP That Cat Owners in the U.S. Should Know?
- CURE FIP™ USA
- Nov 12, 2025
- 6 min read
Feline Infectious Peritonitis (FIP) is one of the most misunderstood yet increasingly treatable diseases in cats. For decades, FIP was considered fatal, but modern antiviral therapy has changed that — thousands of cats around the world have now recovered and are living healthy lives again.
Recognizing the early FIP cats symptoms is critical. The sooner you act, the higher your cat’s chance of recovery. Unfortunately, many cat parents mistake early warning signs for minor infections, which can delay life-saving treatment.
At CureFIP™, we’ve helped more than 87,000 cats worldwide recover from FIP using science-backed antiviral therapy. This guide will help you identify early symptoms, understand the different types of FIP, and know what steps to take next.
What Is Feline Infectious Peritonitis (FIP)?
Feline Infectious Peritonitis (FIP) is a serious viral disease caused by a mutation of the feline coronavirus (FCoV) — not related to the human COVID-19 virus.
Most cats exposed to FCoV develop only mild digestive symptoms, such as soft stool or diarrhea. However, in some cats, the virus mutates inside the body and triggers an abnormal immune response that leads to FIP.
It’s important to know that FIP itself is not contagious. The original feline coronavirus can spread among cats, but once it mutates into FIP, it cannot be transmitted to others. So, a cat with FIP does not pose a risk to other cats in your home.
👉 Read more: Understanding FIP and How CureFIP Treatment Works
Common Early Symptoms of FIP in Cats
So, what are the first feline infectious peritonitis symptoms in cats that every cat owner should look for? Here are the most common early FIP signs, which are often subtle and easy to overlook:
General Early Symptoms (All FIP Types)
Persistent fever that does not respond to antibiotics
Loss of appetite or reduced eating
Weight loss, even when eating normally
Lethargy or reduced activity levels
Rough or dull coat, poor grooming habits
Types of FIP
FIP in cats is classified into two main types — Wet FIP (Effusive) and Dry FIP (Non-effusive).If left untreated, both types can develop into Neurological FIP or Ocular FIP.
Wet FIP (Effusive Form)
Wet FIP occurs when fluid builds up in the abdomen or chest cavity.Cats with this form often appear bloated or pot-bellied, and may have trouble breathing due to fluid pressure.
In some cases, the abdomen feels tight or firm even though fluid is present. Veterinarians can test this fluid to help confirm the diagnosis.
Common symptoms:
Swollen or distended belly
Difficulty breathing or panting
Low energy and loss of appetite
Occasional coughing or weakness
Dry FIP (Non-effusive Form)
Dry FIP affects internal organs such as the liver, kidneys, or lungs without visible fluid accumulation.The affected organs may become firm or enlarged, which can sometimes be detected by gentle palpation during an exam.
Common symptoms:
Gradual weight loss despite normal food intake
Persistent fever and general fatigue
Pale gums or yellowing (jaundice) due to liver involvement
Because Dry FIP progresses more slowly, it’s often diagnosed later than Wet FIP.
Neurological FIP
When FIP affects the central nervous system, it’s referred to as Neurological FIP.Symptoms depend on which part of the nervous system is affected and may include:
Tremors or seizures
Loss of balance or wobbly walking (ataxia)
Muscle weakness or partial paralysis
Behavioral changes or reduced alertness
Difficulty jumping or walking straight
Nystagmus (involuntary eye movement) — increasingly common in neurological FIP cases
Cats with neurological FIP may appear confused, lose coordination, or fall when attempting to walk.
Ocular FIP
Ocular FIP occurs when the virus targets the eyes.This form often presents with visible eye changes such as:
Eye inflammation (uveitis)
Cloudy or color-changed eyes
Reduced or lost vision
Cataracts or inflammation around the iris and lens
Anisocoria (unequal pupil sizes) — one pupil appears larger than the other
Ocular symptoms may appear alone or along with other FIP signs. While supportive care can ease discomfort, antiviral treatment is necessary to stop the disease from progressing.
Early symptoms of FIP in cats include persistent fever, appetite loss, and weight loss. As the disease progresses, cats may develop fluid buildup (Wet FIP), organ inflammation (Dry FIP), or neurological and eye issues.
FIP Symptoms in Kittens vs. Adult Cats
Kittens and young cats (under 2 years old) are at higher risk of developing FIP because their immune systems are still immature.
Signs of FIP in Kittens:
Sudden tiredness or reluctance to play
Failure to gain weight or unexpected weight loss
Swollen, fluid-filled belly
Fast progression from mild illness to severe symptoms
Adult Cats
Adult cats often develop FIP more slowly.They might appear less playful, eat less, lose weight gradually, or hide more frequently than usual.
Because FIP can progress quickly in kittens, even mild symptoms should be taken seriously and checked by a vet right away.
When to See a Veterinarian
If your cat shows persistent fever, appetite loss, or unusual behavior, visit a veterinarian familiar with FIP as soon as possible.
Common diagnostic tests include:
Complete Blood Count (CBC) — checks for inflammation or anemia
A/G Ratio (Albumin/Globulin) — low ratios may indicate FIP
Rivalta Test — assesses fluid in the abdomen or chest
PCR or Immunohistochemistry tests — confirm the virus’s presence
No single test can definitively diagnose FIP, but combining these results with clinical symptoms usually provides strong evidence. Early detection is key — beginning antiviral treatment at the earliest stage dramatically improves recovery rates.
📖 Read more: The First Week of FIP Treatment: What to Expect
What To Do If You Suspect FIP
If you suspect your cat might have FIP, don’t panic — FIP is now treatable and curable.
Your first step should be contacting a vet familiar with modern FIP treatment.Some traditional vets may still believe FIP cannot be cured, but recent data and thousands of success stories prove otherwise.
At CureFIP™, we provide GS-441524-based antiviral therapy — the most effective and scientifically supported treatment for FIP.Our compassionate care team has guided over 87,000 cats globally to full recovery.
Next Steps:
Schedule a vet consultation and discuss FIP-specific testing.
Contact CureFIP™ for expert guidance on treatment protocols.
Monitor your cat’s progress closely during treatment.
👉 Learn more about recovery stories and proven FIP treatment options at CureFIPusa.com.
FAQs About FIP in Cats
1. What are the first signs of FIP in cats?
The first signs usually include fever, loss of appetite, and lethargy. Over time, fluid buildup, weight loss, or neurological and eye symptoms may appear.
2. Can FIP be cured?
Yes. With GS-441524 antiviral therapy, FIP can be fully cured in most cases. Thousands of cats worldwide have recovered through CureFIP™ treatment programs.
3. How long can cats live with FIP?
Without treatment, cats usually survive only a few weeks to months.With early antiviral therapy, recovery success rates now exceed 90%.
4. What should I do if my cat has FIP symptoms?
Visit a veterinarian immediately and contact CureFIP™ for expert guidance.Early diagnosis and treatment are essential for recovery.
5. Is FIP contagious to other cats?
No. While the feline coronavirus can spread, the mutated FIP virus itself is not contagious.
6. Can FIP come back after treatment?
Relapses are very rare, especially when the full treatment course is completed. Post-treatment checkups are recommended.
Conclusion
FIP used to be one of the most heartbreaking diagnoses for cat owners, but today it’s a treatable and curable disease.By recognizing early FIP cats symptoms — such as fever, appetite loss, and bloating — you can act early and give your cat the best chance at survival.
At CureFIP™, we’ve seen thousands of cats make complete recoveries through timely antiviral therapy and dedicated care.
If you suspect FIP, contact CureFIPusa.com today — because early detection saves lives.
If your vet diagnoses your cat with FIP, don’t worry! The CURE FIP™ USA team is ready to help you get the right treatment. You can consult for free with our expert team through:
📲 Instagram: @curefipusa
📘 Facebook: Curefip USA
🎵 TikTok: @curefip
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