UPDATE: See full story here.
The World Health Organization (WHO) today raised the level of influenza pandemic alert from phase 5 to phase 6, the highest.
"The world is now at the start of the 2009 influenza pandemic," said Margaret Chan, WHO Director-General.
As of today, nearly 30,000 confirmed cases of H1N1 influenza A, or swine flu, have been reported in 74 countries.
Earlier today, a report from the journal Nature revealed that this swine flu has been evolving, unnoticed, for years.
Officials caution that this flu is not — at least not yet — as deadly as other viruses involved in past pandemics. While it's impossible to predict for certain how this might play out, the term "pandemic" has more to do with geographic spread than with the killing potential of the bug.
Chan said no other pandemic has been caught in such early stages, and this one is being closely monitored. "We know, too, that this early, patchy picture can change very quickly," she said. "The virus writes the rules and this one, like all influenza viruses, can change the rules, without rhyme or reason, at any time."
Meanwhile, see our main Flu News page for all the news, science and history of this pandemic from the earliest days of the outbreak.