This is from the AP :

Officials reported 20 U.S. cases of swine flu in five states so far, with the latest in Ohio and New York. Unlike in Mexico where the same strain appears to be killing dozens of people, cases in the United State have been mild — and U.S. health authorities can't yet explain why.

"As
we continue to look for cases, we are going to see a broader spectrum
of disease," predicted Dr. Richard Besser, acting chief of the Centers for Disease Control and Prevention. "We're going to see more severe disease in this country."

At a White House news conference, Besser and Homeland Security Secretary Janet Napolitano sought to assure Americans that health officials are taking all appropriate steps to minimize the impact of the outbreak.

Top
among those is declaring the public health emergency. As part of that,
Napolitano said roughly 12 million doses of the drug Tamiflu will be
moved from a federal stockpile to places where states can quickly get
their share if they decide they need it. Priority will be given to the
five states with known cases so far: California, Texas, New York, Ohio and Kansas.

Napolitano
called the emergency declaration standard operating procedure — one was
declared recently for the inauguration and for flooding. She urged
people to think of it as a "declaration of emergency preparedness."

"Really
that's what we're doing right now. We're preparing in an environment
where we really don't know ultimately what the size of seriousness of
this outbreak is going to be."

CDC: http://www.cdc.gov