On 11 June 2009, in response to the global spread of a new strain of H1N1 influenza, the World Health Organization (WHO) declared the outbreak to be an influenza pandemic, the first since 1968. When the outbreak began, U.S. official adopted a response posture under the overall coordination of the Secretary of Homeland Security. This book provides a synopsis of key events in the H1N1 pandemic response, followed by information about selected federal emergency management authorities and actions taken by DHS, HHS, and state and local authorities.