Help needed

[Debbie]

What are the odds of having 15 cats and one tests postive - will the others all 
be postive? These are cats that are strictly indoors now in a 1200 square foot 
house. The infected cat was not outwardly sick and di not socialize with the 
other cats, however they used same litter boxes and ate from same dishes. 
Any help would be greatly appreciated. All cats are close to same age, 
different litters, aquired at the same time.