World Health Organization director general Margaret Chan claps during the opening session of the WHO Summit "Influenza Lessons Learned and Preparedness", in Cancun, Mexico, on July 2, 2009. Getty Images logo Getty Images 32 months ago

World Health Organization director general Margaret Chan claps during the opening session of the WHO Summit "Influenza Lessons Learned and Preparedness", in Cancun, Mexico, on July 2, 2009.