From NPR Health Editor Joe Neel:

NPR ALERT LEVEL: It's still a series of OUTBREAKS in several states and countries. No epidemics, no pandemic.

But WHO raises global pandemic alert level to phase 5 - pandemic is "imminent." And says phase 6 might not be too far away. (That's when they say a pandemic is really happening.)

WEDNESDAY'S EVENTS:

--first U.S death

--WHO declares stage 5 pandemic alert (on a scale of 6)

--Obama says schools should close if suspect or confirm cases of swine flu

--HHS says swine flu vaccine ready by September, if needed

SOME QUESTIONS:

How can we go from pandemic stage 4 to 5 in a day - How is all of this happening so fast? Flu has an incubation period of 24-48 hours. It doesn't take long for it to go from regional clusters to statewide to countrywide and then international. That happens in every flu season. All signs are now pointing to a worldwide swine flu pandemic, but we can't say it's really happening just quite yet.

How deadly will it be? The great 1918 pandemic, which used to be called the "Spanish flu" by the way, had a death rate of 2-2.5%. A smaller world meant 2% of the world's population equals 20 to 40 million dead. Fast forward to our world of 6.8 billion, and that works out to 136 million deaths. That's the worst case. Nobody is predicting that.

But you can see that if the virus is 1% lethal and spreads worldwide, you'd get 60+ million deaths. A serious human tragedy, both in terms of lives lost and economies (futher) devastated.

But so far, there's no way to tell how deadly this H1N1 swine flu virus will be. It might only be 0.1% fatal. Or less, even.