Parents were previously advised to keep their children out of school for seven days after the end of a fever caused by H1N1 . Schools in Chiapas closed , in order to prevent flu resurgence . 1.55 million students affected , 850,000 of them in elementary school . U.S. officials urge restraint when shutting schools , because of flu .
Schools in Chiapas closed , in order to prevent flu resurgence . 1.55 million students affected , 850,000 of them in elementary school . U.S. officials urge restraint when shutting schools , because of flu .