The World Health Organization told its member nations it was declaring a swine flu pandemic Thursday - the first global flu epidemic in 41 years - as infections climbed in the United States, Europe, Australia, South America and elsewhere.
In a statement sent to member countries, WHO said it decided to raise the pandemic warning level from phase 5 to 6 - its highest alert - after holding an emergency meeting on swine flu with its experts.
The long-awaited pandemic decision is scientific confirmation that a new flu virus has emerged and is quickly circling the globe.
CBS News correspondent Richard Roth reports the upgraded classification won't materially change much on the ground in the affected countries. A "pandemic" label is not a statement on the severity of the virus, only on its geographical spread.
CBS News medical correspondent Dr. Jennifer Ashton explained on The Early Show that the would prompt some lagging countries to mobilize resources.
It may trigger drugmakers to speed up production of a swine flu vaccine and prompt governments to devote more money toward efforts to contain the virus.
"Decisions regarding how much vaccine to make and whether or not to recommend it in the general population have not been made yet," Ashton adds.
"At this early stage, the pandemic can be characterized globally as being moderate in severity," WHO said in the statement, urging nations not to close borders or restrict travel and trade. "(We) remain in close dialogue with influenza vaccine manufacturers."
On Wednesday, WHO said 74 countries had reported nearly 27,737 cases of swine flu, including 141 deaths.
The agency has stressed that most cases are mild and require no treatment, but the fear is that a rash of new infections could overwhelm hospitals and health authorities - especially in poorer countries.
Still, about half of the people who have died from swine flu were previously young and healthy - people who are not usually susceptible to flu.
Swine flu is also continuing to spread during the start of summer in the northern hemisphere. Normally, flu viruses disappear with warm weather, but swine flu is proving to be resilient.
The last pandemic - the Hong Kong flu of 1968 - killed about 1 million people. Ordinary flu kills about 250,000 to 500,000 people each year.
Many health experts say WHO's pandemic declaration could have come weeks earlier but the agency became bogged down by politics. In May, several countries urged WHO not to declare a pandemic, fearing it would cause social and economic turmoil.
"This is WHO finally catching up with the facts," said Michael Osterholm, a flu expert at the University of Minnesota who has advised the U.S. government on pandemic preparations.
Despite WHO's hopes, raising the epidemic alert to the highest level will almost certainly spark some panic about spread of swine flu.
Fear has already gripped Argentina, where thousands of people worried about swine flu flooded into hospitals this week, bringing emergency health services in the capital of Buenos Aires to the brink of collapse. Last month, a bus arriving in Argentina from Chile was stoned by people who thought a passenger on it had swine flu. Chile has the most swine flu cases in South America.
In Hong Kong on Thursday, the government ordered all kindergartens and primary schools closed for two weeks after a dozen students tested positive for swine flu - a move that some flu experts would consider an overreaction.
In the United States, where there have been more than 13,000 cases and at least 27 deaths from swine flu, officials at the U.S. Centers for Disease Control and Prevention said the move would not change how the U.S. tackled swine flu.
"Our actions in the past month have been as if there was a pandemic in this country," Glen Nowak, a CDC spokesman, said Thursday.
The U.S. government has already taken steps like increasing availability of flu-fighting medicines and authorizing $1 billion for the development of a new vaccine against the novel virus. In addition, new cases seem to be declining in many parts of the country, U.S. health officials say, as North America moves out of its traditional winter flu season.
Still, Osterholm said the declaration was a wake-up call for the world.
"I think a lot of people think we're done with swine flu, but you can't fall asleep at the wheel," he said. "We don't know what's going to happen in the next 6 to 12 months."