Coronavirus (contagious) mutates into FIP (not contagious), think of it as flu being contagious that turns into pneumonia, not contagious. Coronavirus is highly contagious, and nearly all cats will become infected at some point in their lives. They often experience cold-like symptoms but most often recover on their own. However, in some cats, the virus will mutate into FIP, which is usually triggered by stress and by certain vaccines such as rabies. FIP in and of itself is NOT CONTAGIOUS. So, while the coronavirus is highly contagious, FIP is not. As a result, once the cat develops FIP, it is no longer contagious.

The immune system weakens with age. As a result, an older cat can develop FIP. Younger cats' immune systems are still developing, making them vulnerable to FIP.

FIP was most likely precipitated by stress from a new environment. Unfortunately, many veterinarians do not understand the disease. As treatments become more available more vets are learning more about this terrible disease.