Likely, Sassy wouldn't be contagious to Pretty Kitty, but that would be something your vet could tell you for sure. Pretty Kitty has probably had whatever is causing Sassy's upper respiratory issues and has kicked it. A few years after JD walked up to our house and asked for help, we adopted another stray, Dusty. She didn't catch JD's virus--probably, it was something she'd been exposed to and kicked, like most kitties do. So in case you were wondering, that shouldn't be an issue.