FIP is horrible.

However...there is no test for FIP.

There -is- a test for coronavirus, and some corona positive cats do go on to develop full blown FIP, but it's a very low percentage.

My first bottle baby kitten who I had raised from 3 days old got agressive FIP at 6 months old, and I held him as we euthanized him. Panicked, I spend hundreds of dollars testing my entire household, read up on all the latest studies, retested them...and then decided it was all a load of hooey.

One vet said 95% of cats in the US will light up a corona test, and only a tiny fraction actually get FIP. As my cats share litterboxes, I'd wager that all 8 of them are corona positive, and I'm not remotely worried about it.

As near as anyone can figure, it takes a particular cat's particular immune system reacting to a particular strain of corona to actually get FIP...and so far, nobody has pinned down the specifics on any of those factors. While corona is contagious, FIP is not and most corona positive cats live to a ripe old age and die of normal old-age stuff. Very few will ever get FIP.

Don't sweat it, and don't let the vet tell you otherwise...many of them still believe the older info that FIP is contagious and fatal. The reality is far more complicated than that.