This colorized transmission electron micrograph created in 2009 shows the H1N1 pandemic flu virus that caused a worldwide pandemic in 2009-2010 and since then has become one of the seasonal flu viruses. A 2012 study published in The Lancet Infectious Diseases, Online First estimated that between 151,700 and 575,400 people around the world died from the H1N1 infection during the first year the virus circulated. Centers for Disease Control and Prevention photo by C.S. Goldsmith and A. Balish