HONG KONG - MAY 14:  A passenger is seen wearing a mask at Hong Kong International Airport on May 14, 2009 in Hong Kong, China. Following the 2003 SARS outbreak which was centred around Hong Kong, the country was one of the first to declare Swine Flu as a significant disease, and procedures were immediately put in place by the Food and Health Bureau of Hong Kong on April 26, first issuing warnings not to travel to Mexico and later the same day escalating the alert level from 'alert' to 'serious'. This upgrade activated measures at all entry points to Hong Kong, including temperature and fever screening machines. Getty Images logo Getty Images 6 months ago

HONG KONG - MAY 14: A passenger is seen wearing a mask at Hong Kong International Airport on May 14, 2009 in Hong Kong, China. Following the 2003 SARS outbreak which was centred around Hong Kong, the country was one of the first to declare Swine Flu as a significant disease, and procedures were immediately put in place by the Food and Health Bureau of Hong Kong on April 26, first issuing warnings not to travel to Mexico and later the same day escalating the alert level from 'alert' to 'serious'. This upgrade activated measures at all entry points to Hong Kong, including temperature and fever screening machines.