I've just been talking about how infrequently we actually get D&V type bugs in this household (thank goodness). I can't remember the last time I threw up, probably when I was admitted to hospital with pneumonia 9 years ago.
DD would've been about 12 years ago, DP tends to get migraine type headaches with vomiting more frequently, although not D&V.
I guess our gut flora must be quite robust from drinking tank water containing all sorts of organisms! Plus it helps living fairly remotely and not being in contact with hundreds of bug bearing humans.