The worst illness I've ever had in my life was caught on a plane. A mother with a very sick child seated next to me. She apologized in advance that I was going to get very sick, as her son had the flu and was running a very high fever. She said her whole family had it and it was a bad strain, usually causing high fever and bed rest for a week or more.

I could not change seats. I did the best I could to avoid his sneezes and coughing and hacking. 24 hours later I got a sore throat. 24 hours after that I could not get out of bed. 2 weeks later I finally felt better.

The inconsideration of traveling with a human germ breeder is beyond my comprehension.

I'm not sure in a such a situation that you can avoid getting sick. I'm a pretty healthy guy, and that one really side-lined me for a few weeks.