This colorized image from a transmission electron micrograph (TEM) depicts the A H1N1 "swine flu" virus from a previous outbreak in 1976, in an image released by the U.S. Centers for Disease Control (CDC), April 24, 2009. A deadly strain of flu never seen before has killed as many as 61 people in Mexico and has spread into the United States, where several people were reported ill. REUTERS/Dr. Erskine Palmer and R.E. Bates/Centers for Disease Control/Handout (UNITED STATES HEALTH IMAGE OF THE DAY TOP PICTURE) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS
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