A 1992 study found the following: 400 kittens were divided into 41 household with various FIP histories. In one group the kittens were allowed to freely associate with all the cats. In a second group the kittens were isolated only with their mother. In the third group, the kittens were isolated by themselves starting at age 2-6 weeks. Only in this last group did all of the kittens remain seronegative for any/all coronaviruses.