I wonder if the bunker people are the ones who introduced the virus? Either intentionally or accidently. Though if they know they're immune, why the gas masks?
Anyway, as much as I as cringed while watching the show (Tandy mostly), I'm glad they found a large group of survivors, and I hope it is a peaceful joining. With three babies and two on the way, I don't think even this show would have something too awful happen to the gang.