LOL. Japanese people always wear masks because they think it prevents them from catching cold and influenza.
I arrived in Japan in January a few years ago and I noticed in Kansai Airport a lot of people were wearing masks. I thought it was the bird flu, but its just a country full of people with obsessive compulsive disorder. LOL. The Japanese are just like the Germans.
In my office one of the ladies who always, always wears a mask was the only who's gotten the H1N1 virus. Ha ha.