ABC’s Hanna Siegel from New York: If you were to look out onto the streets of Mexico today you might think you were in an operating room, surrounded by doctors in surgical masks. But you’d just be looking at concerned citizens, trying to keep the dreaded swine flu at bay. And the masks aren’t only being used in Mexico. Just yesterday, a friend of mine traveling from New York City — where just last night a new case of the virus was confirmed — to Florida, was given a mask and a pair of gloves just in case. And today, one of our senior producers went to get a haircut only to be faced with a hairdresser wearing…you guessed it, a mask. But do the masks really work? Is covering your nose and mouth the key to evading the swine flu and other germs? To find out, ABC’s Sharyn Alfonsi dissected the science of a sneeze this morning on Good Morning America. It turns out when you sneeze the air comes out of your nose at one hundred miles per hour releasing germs into the air. From there, the germs can travel anywhere from three to one hundred and fifty feet in front of you, giving them a chance to infect plenty of innocent bystanders. But, whether or not you become infected could actually depend on the weather. As Sharyn reported, the flu virus leaves your body encased in tiny droplets of water that shoot out of your nose when you sneeze (hence the mini shower you get if anyone sneezes on you). So if the weather is humid, the moisture in the air attaches itself to those droplets and drags them down, towards our feet where we can’t become infected. But, if the air is cool and dry, those droplets can float along higher up, putting them face to face with someone else’s nose and mouth. Or their mask. So does the mask provide adequate protection? Well, yes and no. Germ expert Dr. Elaine Larsen, who talked to Sharyn this morning, says the masks can serve as a good barrier but only up to a point. After a few hours, they start to get saturated and turn into a sponge-like device, potentially holding in germs it encounters and causing you to breathe them in. So the answer is yes, the masks do work. But the key to avoiding the germs entirely is changing your mask regularly…and maybe hoping for a rainy day.