If you've noticed you frequently get sick on vacation, there are good reasons for that -- lots of 'em. 

Dr. Herbert DuPont is director of Houston's UT School of Public Health Center for Infectious Diseases and on staff at Baylor-St. Luke’s Medical Center. He says vacation meals are typically at restaurants.

"You know when you eat just a portion of your meals at home you have lots of protection against microbes in food from restaurants. That actually does save you from becoming ill."

Dr. DuPont says another big factor is being on public transportation and in public places where lots of people can spread their germs to you.

"Then you're in close proximity to other people who have colds and viral infections and so you pick them up. So you're really doing everything possible to promote symptoms and minor infections."