My sick relatives

Grandma, who lives in Texas along with most of the rest of my extended family, frequently sends emails to the family mailing list containing the latest news from home. Almost invariably, the latest news from home involves at least one branch of the family being sick with colds, fevers, viruses, or various other ailments. Meanwhile, I think I've been sick maybe twice in the last two years, and it wasn't anything remotely serious either time. I can't even remember the last time I had a cold, and it's been ages since I set foot in a doctor's office for an actual physical ailment.

At first I thought it was because my relatives have small children who are likely in school with disease-carrying rapscallions, but when I think back to my younger days, I still can't remember being sick nearly as often as my relatives seem to be. The only possible explanation I can think of (though not a scientific one by any means) is that there's something about Texas that is making my poor relatives more susceptible to diseases, while I'm sitting up here in Oregon in perfect health.

Where would one find statistics on this sort of thing? Are people who live in the south — or perhaps in warmer or more humid climates — really more prone to disease?