MEXICO CITY - Mexico reported no new deaths from swine flu overnight - more reason to be optimistic that the worst is over at the epicenter of the outbreak. But the virus keeps spreading around the world, with new cases confirmed in Latin America, Europe and Asia, and governments banning flights and preparing quarantines.
The World Health Organization said it has sent 2.4 million treatments of anti-flu drug Tamiflu to 72 developing countries, taking the drugs from a stockpile donated by Roche Holding AG.
'At this point it's important that all countries have access to antivirals,' said Dr. Mike Ryan, WHO's global alert and response director.
The WHO has decided not to raise its alert to a full pandemic, since the virus has yet to cause sustained transmission outside North America. But Ryan warned against complacency.
'These viruses mutate, these viruses changes, these viruses can further reassort with other genetic material, with other viruses. So it would be imprudent at this point to take too much reassurance' from signs the virus is weaker than feared.
The U.S. Centers for Disease Control and Prevention also said it's too early to declare victory.
'We have seen times where things appear to be getting better and then get worse again,' said Dr. Anne Schuchat, the U.S. agency's interim science and public health deputy director. 'I think in Mexico we may be holding our breath for sometime.'
Costa Rica reported its first confirmed swine flu case - and the first flu case in Latin America outside Mexico.
And China worked aggressively to track down people who may have been near a sick Mexican tourist, sealing 305 people inside a Hong Kong hotel where he stayed and hospitalizing 15 fellow passengers. The man developed a fever after arriving in the Chinese territory and was isolated in stable condition Saturday.
South Korea reported Asia's second confirmed case - a woman just back from Mexico - and other governments also prepared to quarantine passengers, eager to show how they have learned from the deadly SARS epidemic in 2003, when Hong Kong was criticized for imposing quarantines too slowly.
The U.S. is taking 'all necessary precautions' now to be prepared if the swine flu develops into 'something worse' President Barack Obama said Saturday.
'This is a new strain of the flu virus, and because we haven't developed an immunity to it, it has more potential to cause us harm,' Obama said. 'Unlike the various strains of animal flu that have emerged in the past, it's a flu that is spreading from human to human. This creates the potential for a pandemic, which is why we are acting quickly and aggressively.'
The global caseload was 718 and growing - the vast majority in Mexico, the U.S. and Canada.