In the past five years I've had three multi-week overseas vacations where I've had to take a week or more off sick from work immediately on returning home. Each

In the past five years I've had three multi-week overseas vacations where I've had to take a week or more off sick from work immediately on returning home. Each of those years, that was my only time that year getting sick. I assume travelling just exposes us to more people, more unsanitary situations, and more opportunities to wear down our immune systems.