This undated photo from the journal Science shows Dr. Terrence Tumpey, a microbiologist for the U.S. Centers for Disease Control and Prevention’s National Center for Infectious Diseases, examining specimens of the 1918 pandemic influenza virus -- a virus that was reconstructed in hopes of combating a future flu pandemic. The flu pandemic of 1918-1919 killed between 20 million and 40 million people and has been called the most devastating epidemic in recorded history. (© AP Images)