Getting sick while on vacation is MUCH more common than while at home. Doctors loosely call it "travelers' illness" or something like that. Getting sick while traveling is more likely than while at home for several reasons: your immune system is not functioning as efficiently due to stress and perhaps more exercise (walking) than you're used to; you tend to be slightly dehydrated; and you encounter "foreign" bacteria. Our immune systems are pretty good at fighting germs they've encountered before, but they kinda stink at fighting "foreign" germs, meaning germs they've never seen before. This means that if you go to a different region, you are more likely to be exposed to germs your immune system has never seen before, and therefore it's easier to get sick. That problem is compounded a thousand times over at a vacation mecca such as WDW, where you not only have the local central Florida germs, but you also have germs imported from all over the world by those 34 million tourists every year.
But people usually don't take that into account when they get sick on vacation. They tend to blame food and ONLY food. There are PLENTY of viruses out there that cause GI upset, and not all of them are food-borne. But catching a germ from touching a surface is "invisible," so we don't even know it happened. But we remember eating a burger, so we blame the burger.
Problem is, that's not always the case.