Authorities in Mexico say they're ecouraged by a drop in the number of people being admitted to hospital with symptoms of swine flu. That cautiously optimistic tone comes as May Day rallies and other celebrations aroud the country have been cancelled to avoid spreading the swine flu virus. The holiday break coincides with a government call on people to stay at home for five days as health experts continue efforts to contain the virus and work out whether there is any pattern to how it is spreadin