Nuns of the Santa Ines Virgen y Martir convent listen to the Sunday mass over the radio in Tlalpan, Mexico City April 26, 2009. Fears of a global swine flu pandemic grew with new infections in the United States and Canada on Sunday, and millions of Mexicans hid indoors to avoid a virus that has already killed up to 81 people. Mexico City, one of the world's biggest cities, practically ground to a halt on Sunday with restaurants, cinemas and churches closing their doors and millions staying at home as officials tested 1,300 suspect cases. REUTERS/Jorge Dan (MEXICO ENVIRONMENT HEALTH RELIGION)