An airport staff supply face mask and propaganda paper to a visitor at Hong Kong International Airport in Hong Kong, south China, on May 1, 2009. The authority of Hong Kong has raised the flu alert level from "serious" to the highest level of "emergency" as a 25-year-old Mexican man who arrived here via Shanghai was confirmed the first case of influenza A/H1N1 infection in the city on Friday. [Xinhua]

Staff of Hong Kong International Airport wear face masks as they serve a visitor in Hong Kong, south China, on May 1, 2009. [Xinhua]