FIP, or Feline Infectious Peritonitis, is a viral disease that affects cats, caused by certain strains of the feline coronavirus. It primarily targets the cat's immune system and can lead to severe inflammation in various organs. Symptoms may include fever, weight loss, and fluid accumulation in the abdomen or chest. There are two forms of FIP: the wet form, which involves fluid buildup, and the dry form, characterized by granulomas in organs. Diagnosis often requires veterinary evaluation, and while FIP was once considered fatal, recent advancements in treatment have shown promise in managing the disease.