I consider myself lucky so far, no dive trips cancelled due to health. However, I've been at this less than a year so I know my chance is coming. Most the time I could live with it, but we've had a couple of Caribbean trips where I've gone around the week before chanting... "can't get sick", "can't get sick". I couldn't imaging much worse than having a nice week of diving planned in a warm climate, then getting sick! Yuck.