Paloma Heya Nina!Honestly, do your best to simply not worry. The chcanes are so slim of you contracting the virus. I ride the New York subway system daily (what a cesspol of viruses THAT is), and I am not concerned.Where are you planning to travel to? Even most of Mexico is not high risk, outside of Mexico City.The main thing that will help is simply washing your hands frequently. And maintain consciousness of not touching your hands to your face after touching something lots of other people have touched, like a pole on the metro, until you've washed.Masks apparently do almost nothing. Don't bother.I wish I could find a journalist's article I read about it, who lived through SARS in China. That was her advice washing your hands frequently does a surprising amount to cut down the rate of infection for such a virus. And not just SARS or swine flu, but pretty much all viruses. While masks were not very effective at keeping the uninfected from contracting the virus. They only help the sick from spreading the germs around. So if you're healthy, masks don't make any sense.Anyway, enjoy your trip and don't stress! Stress lowers your immune system! :-p