The Geneva-based media officer is one of the more active voices of the World Health Organization and frequently covers bird flu and other epidemics. Within the last year, his feed has largely focused on the H7N9 outbreak in China, Middle East Respiratory Syndrome (mostly in Saudi Arabia) and the Ebola outbreak in Guinea. Easily reachable by email or tweet, he promptly replies to questions about disease and frequently posts the latest WHO releases and figures. —Andrew Katz