The number of confirmed influenza A (H1N1) cases in Japan exploded over the weekend, going from an officially reported four—all in returning vacationers—on 16 May to 129 as of 18 May. The 125 new cases are all among high-school students in Osaka and Kobe, two neighboring cities in western Japan. None of these cases has yet been linked to a returning traveler. Japanese media, citing their own surve