In 2003, during the severe acute respiratory syndrome epidemic, 76 percent of Hong Kong residents wore simple masks, and in this case, mask use was associated with a lower incidence of SARS, as well as upper respiratory tract infections and influenza.

CNN: Commentary: Flu and your health on a plane

Do you remember back in 2003, when practically everyone traveling to and from Asia was wearing a mask and there was a travel advisory in affect over a new mysterious disease known as SARS?

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The suspect behind SARS, a coronavirus, is smaller than that but comes encased in water droplets that get caught outside the mask.

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