If you were on the street in Mexico today you might think you were in an operating room, surrounded by doctors. You could see many concerned people with masks   trying their best to stop the swine flu  . And the masks aren't only being used in Mexico. A friend of mine traveling from New York City to Florida was given a mask and a pair of gloves just after he reached the airport. And another friend went to get a haircut only to be faced with a hairdresser wearing a mask! But do the masks really work? Is covering your nose and mouth the key to stopping the swine flu? To find out the truth, ABC's reporter Sharyn Alfonsi talked with germ   expert Dr. Elaine Larsen. It turns out that when you sneeze   the air coming out of your mouth at a speed of one hundred miles per hour carries germs which can travel anywhere around you and make people around you infected  . However, whether you become infected actually depends on the weather. As Sharyn reported, when you sneeze, the germs leave your body in small drops of water coming out of your mouth. If the weather is wet, the wet air will make the small drops bigger and heavier and they drop down towards our feet. If this happens, we won't become infected. But if the air is dry, those small drops can float higher up, making it possible for them to touch someone else's nose, mouth or their mask. Larsen says the masks can stop the germs well but after a few hours, they start to get wet, holding a lot of germs they come across and causing you to breathe them in. The masks do work, but the key to stopping the germs is changing your masks often. What should we pay attention to when wearing masks?
Keeping the masks dry. Changing the masks often. Choosing very thick masks. Wearing big masks.