This statement was just released by acting Health and Human Services Secretary, Charles E. Johnson 

“As a consequence of confirmed cases of Swine Influenza A (swH1N1) in California, Texas, Kansas, and New York, on this date and after consultation with public health officials as necessary, I, Charles E. Johnson, Acting Secretary of the U.S. Department of Health and Human Services, pursuant to the authority vested in me under section 319 of the Public Health Service Act, 42 U.S.C. § 247d, do hereby determine that a public health emergency exists nationwide involving Swine Influenza A that affects or has significant potential to affect national security.”

Released: April 26,2009 / http://www.hhs.gov/secretary/phe_swh1n1.html