MEXICO CITY (AP) — At least 16 people — and possibly dozens more — have died from a swine flu virus in Mexico, and world health officials worry it could unleash a global flu epidemic. Mexico City closed schools across the metropolis Friday in hopes of containing the outbreak, and tougher measures were being considered.Scientists were trying to determine if the deaths involved the same new strain of swine flu that sickened seven people in Texas and California — a disturbing disease that combines pig, bird and human viruses in a way that researchers have not seen before.The World Health Organization counted at least 57 deaths in Mexico, but said it wasn't yet clear what flu they died from."We are very, very concerned," WHO spokesman Thomas Abraham said. "We have what appears to be a novel virus and it has spread from human to human."WHO raised its internal alert system Friday, enabling the agency to divert more money and personnel to dealing with the outbreak. "It's all hands on deck at the moment." Abraham said.President Felipe Calderon cancelled a trip and met with his Cabinet to coordinate Mexico's response. The government has 500,000 flu vaccines and planned to administer them to health workers, the highest risk group.There are no vaccines available for the general public in Mexico, and authorities urged people to avoid hospitals unless they had a medical emergency, since hospitals are centers of infection. They also said Mexicans should refrain from customary greetings such as shaking hands or kissing cheeks.But the U.S. Centers for Disease Control and Prevention said Americans need not avoid traveling to Mexico, as long as they take the usual precautions, such as frequent handwashing.Mexico's Health Secretary, Jose Cordova, said only 16 of the deaths have been confirmed as the new swine flu strain, and that government laboratories were testing samples from 44 other people who died. At least 943 nationwide were sick from the suspected flu, the health department said.Morehttp://www.google.com/hostednews/ap/articl...zMM_EQD97P008G2