FILE - In this Thursday, May 1, 2003 file photo, passengers wearing masks sit in a bus in Hong Kong to protect themselves from severe acute respiratory syndrome, or SARS, that has killed at least 162 people in Hong Kong. The scenes now unfolding in Mexico City are familiar ones to this region. Years before the swine flu outbreak, Asia dealt with two major public health emergencies back-to-back, SARS and bird flu. Both crises offered lessons that have helped China , Vietnam and other countries in the region prepare for the emergence of the latest global epidemic, experts and officials say.