After weeks—or even months—of anticipation, you have finally made it to your destination and are ready to enjoy a few days of sun, sand, and sangria. But wait, is that a sniffle in your nose, a scratch in your throat?

Though it is unpleasant and can even feel downright unfair, coming down with a bug during your time off isn’t uncommon. And of course, it’s certainly possible to catch a cold in the crammed quarters of a plane or eat something that makes your digestive system say, “No, thanks.” But sometimes your immune system simply decides to take a break right along with the rest of you—and that’s not necessarily a coincidence.

This phenomenon has a name: leisure sickness.…