IS FIP CONTAGIOUS?Very simply, the answer is no.SO HOW CAN AN INFECTIOUS DISEASE NOT BE CONTAGIOUS?Feline Infectious Peritonitis is a reaction to infection with the feline coronavirus. Most cats who become infected with the feline enteric coronavirus (often simply called "feline coronavirus") essentially get the flu and never develop anything that can in any way be described as serious. Some cats, however, react with this devastating syndrome.WHAT DO WE KNOW ABOUT THE FELINE ENTERIC CORONAVIRUS?Here are some basics about this virus:It is common wherever cats are housed in groups and it is readily transmitted between cats.Transmission is typically by contact with infected feces. This means that the litter box is the usual place where infection takes place. This infection is unusual in cats that free-roam outdoors (no litter box) or who live in homes where there is only one cat. The virus enters the new host's body via the nose and mouth.An active infection lasts several weeks to a few months. Virus is shed in the infected cat's stool during this period. If the cat is reinfected, virus sheds again for weeks to months. During this time, the cat may or may not seems at all ill. Some infected cats do not shed virus.Households with fewer than 5 cats eventually spontaneously clear of coronavirus. Households with more than 5 cats virtually never clear of coronavirus.Most household disinfectants readily kill coronavirus immediately. Room temperature kills coronavirus within 48 hours. Carpeting is protective to the virus and the virus is able to survive in carpeting for at least 7 weeks.Once a cat has been infected with the virus and recovered, the cat can be easily re-infected by continued exposure to infected feces. In this way, many catteries where there are always cats sharing litter boxes never rid themselves of this infection.The enteric coronavirus attacks intestinal cells and creates GI upset. As the long as the infection is confined to the GI tract, there will be no FIP.The process of immunological defeat of the virus involves a cell called a "macrophage." The macrophage consumes infected material, packaging it in special structures which it floods with acids and digestive enzymes. Any virus is killed by this process and its components are then used by the immune system to help mount a specific immunological reaction (i.e. make the proper antibodies, send specific killer cells etc.) In some cats, a mutation occurs in the coronavirus. This mutation occurs during infection and allows the virus to survive the treatment by the macrophage. Instead of being killed by the macrophage, the virus essentially uses the macrophage to hitch a ride into the body's core. The macrophage response mounts in an attempt to kill the virus but ends up producing heaps of ineffective macrophages and immunologic proteins which make up a special immunologic tissue called a "pyogranuloma." FIP is basically the infiltration of normal organs with pyogranulomas. The mutation to a form of virus that can cause FIP is more likely to occur in a cat with an immune-compromise. Most cats with FIP are under age 1 year (their immaturity being their immune-compromise). Crowding is also an important source of immune-compromise. WHY ISN'T THE MUTATED VIRUS CONTAGIOUS?We do not know why. We can inject fluids from a cat with FIP into a normal cat and cause FIP but short of this kind of experimental transmission, the mutated virus doesn't seem to make into the natural external secretions of an infected cat. This effectively confines the mutated virus inside the sick cat's body, though the sick cat will still shed non-mutated virus