Students spray hand sanitizer before attending classes at the National Autonomous University of Mexico (NAUM) in the Mexico City on May 7, 2009. All high schools and universities in Mexico resumed classes on Thursday as the government said the worst of the flu crisis is over. [Xinhua]

Students wearing masks attend a class at the National Autonomous University of Mexico (NAUM) in the Mexico City on May 7, 2009. [Xinhua]