More than 80 people have died and more than 1,300 suspected cases exist in Mexico in the swine flu outbreak that has emergency-preparedness personnel swinging into action around the globe.

According to the World Health Organization, the swine flu strain has been confirmed in 18 people in Mexico and 20 in the United States, including cases in New York City, Ohio, Kansas, Texas and California. Suspected cases are being investigated from New Zealand to Spain.

Richard Besser, acting director for the US Centers for Disease Control and Prevention, said on Sunday that as doctors look for more cases of the disease, he expects those numbers to rise. In a press conference from the White House, he and Department of Homeland Security director Janet Napolitano sought to reassure the US public that officials were monitoring the outbreak. The strain appears to be resistant to two common flu drugs but is susceptible to the newer drugs Tamiflu and Relenza. US officials have ordered the release of one-quarter of the nation’s emergency stockpile of 50 million doses of these drugs, to be given preferentially to states with confirmed cases of the disease.

Mexico has closed down schools in and around Mexico City, and urged people to stay home and wash their hands.

The World Health Organization’s influenza pandemic alert system remains at 3. Raising it to a 4 would reflect “sustained human-to-human transmission” reflecting “community-level outbreaks”.

Hong Kong, still reeling from its experience with the SARS epidemic, on Sunday ordered anyone who felt sick and had traveled through affected areas in the past seven days to go to a hospital.

The H1N1 strain contains genetic contributions from human, swine and avian influenza.