How the Flu Decider Decided

/Laurent Gillieron/AP/Keystone

WHO's Margaret Chan: The Pandemic Decider has decided

Even the most labored decision has a tipping point—a moment when the mountain of evidence suddenly shifts in the same direction. NPR's Richard Knox was on a conference call with WHO's chief Margaret Chan this morning when she announced that (finally!) she'd decided to declare the H1N1's spread around the world worthy of the designation "pandemic."

So, how did she decide? Knox says,

She ducked questions about what new evidence has emerged in the past few days to precipitate a declaration of something that many public health experts have said is obvious. The tipping point is widely thought to be the spread of flu in southern Australia, where more than 1,200 cases of the new flu have been counted in a matter of days.

Or, Knox says, maybe it was new spurt of cases in the United Kingdom, or the way the pandemic virus is rapidly crowding out other strains in Chile, which is just now entering it's winter flu season.

Look for more insights on what's next with the pandemic from Richard Knox tonight on All Things Considered.