Feline infectious peritonitis (FIP) is a viral disease that occurs worldwide in wild and domestic cats. There are two forms of the disease: wet form and dry form. In households containing only one or two cats, the FIP mortality rate is around one in 5,000. The vaccine appears to be safe, but the risks and benefits of vaccination should be weighed carefully. Confirming a diagnosis of FIP can actually be very difficult. The best method to confirm a diagnosis of FIP requires a veterinarian taking a biopsy. Cats infected with FeCV usually do not show any symptoms during the initial viral infection, but may occasionally experience brief bouts of diarrhea and/or mild upper respiratory signs from which they recover spontaneously. While antibody levels, or titers, to coronavirus can be measured, they cannot definitively distinguish between exposure to FeCV and FIPV. Feline infectious peritonitis or FIP in cats is an immune reaction to the infection of feline coronavirus (FCoV). They are equally tricky to diagnose. Litter boxes should be kept clean and located away from food and water dishes. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet. Most cats infected with the virus causing FIP will never become ill, but cats who do develop signs of FIP will always succumb to the disease. Cats that have been initially exposed to FeCV usually show no obvious symptoms. When this occurs, the virus is referred to as the FIPV. Some studies show that it protects against disease, while others show that it offers little benefit. This is particularly true if characteristic fluid (yellow tinged with a high protein and white blood cell concentration) begins to accumulate within body cavities. It is caused by a type of virus called a coronavirus, which tends to attack the cells of the intestinal wall. In 1970, the coronavirus that causes FIP was isolated and characterized. A 1994 study reported that cats with signs suggestive of FIP, who also had a high coronavirus antibody level, reduced numbers of lymphocytes and high levels of globulins in the bloodstream, had an 88.9 percent probability of having FIP. Other available tests can, in theory, detect the presence of the virus itself. Any cat that carries FeCV is potentially at risk for developing FIP, but younger cats are at greater risk of developing FIP, with approximately 70% of cases diagnosed in cats less than 1 1/2 years of age and 50% of cases occurring in cats less than 7 months of age. Some cats may show mild upper respiratory symptoms such as sneezing, watery eyes, and nasal discharge, while others may experience mild gastrointestinal signs such as diarrhea. The mutated virus is not shed by the cat, so while FIP is not actually contagious, the more benign feline coronavirus is contagious to other felines. Despite the claims made by some laboratories and test manufacturers, there is currently no test that can distinguish between the harmless intestinal coronavirus and the deadly FIP coronavirus. This is particularly true of cats that are housed in high density (shelters, catteries), and housing cats at a density at or below three per room is recommended to minimize stresses that can be associated with crowded living conditions. A variety of medications designed to reduce the abnormal immune response to the virus or reduce the ability of the virus to reproduce have been tried and may provide some relief from the disease and prolong survival. Generally speaking, the signs of the noneffusive form, which may include the non-specific signs listed above as well as neurologic signs including seizures and ataxia (abnormal or uncoordinated movements) develop more slowly than those of the effusive form. Cats with fluid in the abdomen show progressive, nonpainful abdominal distension. Most strains of feline coronavirus are found in the gastrointestinal tract and do not cause significant disease. It causes abdominal distension and/or difficulty breathing. Granulomas in the eye may cause the pupil to appear irregular and the eye to appear discolored.