What is feline infectious peritonitis (FIP)?

Feline infectious peritonitis (FIP) is a disease caused by a feline coronavirus. Only a small percentage of cats who get infected with the virus develop FIP. FIP can cause general symptoms such as weight loss and fever. It can also lead to many other issues, including eye problems.

Cause of FIP in Cats

Feline infectious peritonitis is caused by the feline enteric coronavirus (FeCV). Many cats get infected with this coronavirus as kittens or young adults. In most cats, the virus never causes any lasting problems. 

A cat may develop mild symptoms shortly after getting the virus. These may include diarrhea,  respiratory issues, watery eyes and eye discharge. These symptoms usually clear up quickly.

In about one in 10 cats, the virus changes in ways that allow it to infect macrophages, which are specialized immune system cells. Most cats fight off this infection, and fewer than 2% develop FIP. 

In these cats, the virus can travel through the blood to affect different parts of the body, including the eyes. Most cats that get diagnosed with FIP are under three years old.

You should know that FeCV is a feline coronavirus. It's not the same as the coronavirus that causes COVID-19 in humans. FeCV is more similar to some of the coronaviruses that cause common colds in humans. But this coronavirus is specific to cats.