Cats with Rhinosinusitis

I have 4 cats - all obtained from rescue shelters. My latest addition has Chronic Sinusitis. I've been keeping it under control with daily L-Lysine amino acid supplements and a stress-free environment. He has not passed it to my other cats since they were vaccined when they were young. Now I'm thinking about getting another cat but this time, it would be a kitten since I've always adopted older cats. I've read that kittens are very suceptible to this virus and I would like to know if there are preventive steps that I can take or if I just can't have a kitten because the risks are too great.

Please do NOT bring another kitten into your home until your cat is completely well. Kittens are VERY susceptible to this and have weak defenses to fight it - they often die from it since cats have no reserve and absolutely need to eat. Colds affect their significant sense of smell and thus their desire to eat, a recipe for disater in any kitten, however healthy.