On June 11, 2009, in response to the global spread of a new strain of H1N1 influenza ("flu"), the World Health Organization (WHO) declared the outbreak to be a flu pandemic, the first since 1968. Officials believe the outbreak began in Mexico in March, or perhaps earlier. The novel "H1N1 swine flu" virus was first identified in California in late April. Since then, cases have been reported around the world. The H1N1 pandemic virus is a reassortment of several existing strains of influenza A, subtype H1N1 virus, including strains typically found in pigs, birds, and humans. Since the H1N1 pandemic virus emerged in the spring, the U.S. Centers for Disease Control and Prevention (CDC) has continued the operation of U.S. seasonal (routine) flu surveillance systems, which are normally suspended during the summer. These systems track trends in rates of illness and hospitalization but are imprecise in their accounting for the total numbers of deaths and hospitalizations due to the pandemic. CDC has published an estimate of these counts, stating that between April and October 17, there were between 14 million and 34 million cases of H1N1 infection, between 63,000 and 153,000 H1N1-related hospitalizations, and between 2,500 and 6,000 H1N1-related deaths in the United States. (See " CDC: Disease Surveillance, and Estimates of Illnesses and Deaths .") The CDC reports that the symptoms and transmission of the novel H1N1 flu from person to person are generally similar to seasonal flu. Laboratory testing of the new strain indicates that the antiviral drugs oseltamivir (Tamiflu) and zanamivir (Relenza) are generally effective in treating illnesses caused by the pandemic strain. In contrast to seasonal flu, the pandemic strain appears to cause serious illness more often among children, and less often among the elderly. However, like seasonal flu, pregnant women and individuals with serious chronic diseases appear to be at greater risk of serious illness from the pandemic strain. In response to the outbreak in April, Janet Napolitano, Secretary of the Department of Homeland Security (DHS), assumed the role of Principal Federal Official, coordinating federal response efforts. Charles E. Johnson, then the Acting Secretary of Health and Human Services (HHS), declared a public health emergency, which remains in effect. Among other things, this has allowed the Food and Drug Administration (FDA) to issue Emergency Use Authorizations (EUAs), permitting certain unapproved uses of antiviral drugs (such as in very young children) and some types of protective facemasks, the use of unapproved diagnostic tests for the new flu strain, and the use of the unapproved antiviral drug peramivir. HHS has established a government-wide informational website ( www.flu.gov ) with information for planners, health care providers, and the public. On October 24, President Obama declared the pandemic to be a national emergency, which allowed waivers of some requirements under Medicare and Medicaid law to help health care facilities manage increased numbers of patients. To date, there has not been a presidential declaration regarding the pandemic under the Robert T. Stafford Disaster Relief and Emergency Assistance Act (the Stafford Act). The applicability of this Act to infectious disease incidents is unclear. (See " Key Federal Government Authorities and Actions " and Figure 1 , "Selected Federal Emergency Management Authorities Applicable to the H1N1 Influenza Pandemic.") Many U.S. communities closed schools when students were found to be infected with the new flu strain. School closure decisions, made by local officials, were based on initial CDC guidance, which was revised as it became clear that the virus was in wide circulation, and that the illnesses it caused were generally mild. CDC now recommends against routine school closures when small numbers of students are infected, arguing that such closures may do little to reduce the spread of the virus, while placing a considerable burden on the affected community. (See " Pandemic Preparedness and Response in Schools .") The U.S. response to the pandemic triggered a slate of plans that were developed, beginning around 2004, to address concerns about the global spread of another novel flu strain, the H5N1 avian flu. (See box below for definitions.) In FY2006 supplemental appropriations, Congress provided $6.1 billion for pandemic planning across several departments and agencies. These earlier efforts, and others aimed at preparedness for bioterrorism and emerging infections in general, have generally streamlined the response to the H1N1 pandemic. To address the H1N1 outbreak, the Obama Administration requested $2 billion in FY2009 emergency supplemental appropriations, and transfer authority for an additional amount of almost $7 billion from existing HHS accounts. On June 26, the President signed P.L. 111-32 , which provided $1.9 billion in FY2009 supplemental appropriations immediately, and an additional $5.8 billion contingent upon a presidential request documenting the need for additional funds. The President has twice requested portions of the contingent funding. (See " Appropriations and Funding .") A voluntary national pandemic vaccination campaign is underway. In June, HHS Secretary Kathleen Sebelius issued a declaration waiving liability and enabling a compensation program in the event that injuries result from use of pandemic vaccine. CDC has developed recommendations for groups of individuals who should be given priority for vaccine when it is available in limited amounts. Costs associated with the vaccination program are being funded through both public and private sources. Vaccine is being provided to states as it becomes available, according to states' populations. Vaccine delivery is carried out by a CDC contractor. Decisions regarding vaccine distribution to health care providers, clinics, schools, and other vaccination sites are the responsibility of state and local governments. There have been a number of problems associated with shortfalls of actual (versus predicted) vaccine availability, and charges that vaccine would not be available for most of the individuals in designated priority groups until after the peak of pandemic virus transmission had passed. (See " Vaccines and Pandemic Influenza .") This report provides information about selected federal emergency management authorities and actions taken by DHS and HHS, and actions taken by state and local authorities, in response to the pandemic. It then lists congressional hearings held to date; provides information about appropriations and funding for pandemic flu preparedness and response activities; summarizes U.S. government pandemic flu planning documents; and lists sources for additional information about the pandemic. An Appendix describes the WHO process to determine the phase of a threatened or emerging flu pandemic, and touches on several related issues. All dates in this report refer to 2009 unless otherwise specified. This report will be continually updated to reflect unfolding events. Under current law, the Secretary of Homeland Security leads all federal incident response activities, while the Secretary of HHS leads all federal public health and medical incident response activities under the overall leadership of the Secretary of Homeland Security. The Government Accountability Office (GAO) has noted, in the context of pandemic flu planning, that "these federal leadership roles involve shared responsibilities between [HHS] and [DHS], and it is not clear how these would work in practice." GAO recommended that HHS and DHS conduct training and exercises to ensure that federal leadership roles are clearly defined and understood. As recently as July 2009, GAO testified that although some recommended exercises had been undertaken, it was unclear whether they rigorously tested federal leadership roles in a pandemic. GAO also recommended, among other things, that federal pandemic plans published in 2006 be updated. In July, DHS Deputy Secretary Jane Holl Lute testified that an implementation plan for response to the current pandemic was being finalized under the leadership of the National Security Council. In August, the President's Council of Advisors on Science and Technology (PCAST) released a report assessing preparations for a possible resurgence of H1N1 flu and recommending additional actions. PCAST also noted the potential ambiguity in the leadership roles of DHS and HHS, and recommended that the Homeland Security Advisor be given primary responsibility for decision making during the pandemic response, saying: The Working Group has some concerns, based on conversations with representatives of the various agencies involved, that decision-making authorities and processes may not be completely clear in all cases. Primary Federal responsibilities for response to an epidemic are lodged in two departments ([HHS] and DHS), with significant involvement of others (Education, Defense, State, Agriculture, Labor), and coordination by White House staff. While the National Strategy for Pandemic Influenza Implementation Plan provides a comprehensive list of assignments for a multitude of offices, agencies, and departments involved in the Federal planning process, the large number of tasks and responsible units tends to obscure the primary seat of responsibility.... The Working Group believes it would be valuable to clarify these matters before events accelerate in September and assign to the Homeland Security Advisor the responsibility for ensuring that all of the important decisions are made in a timely fashion and with appropriate consultation with the President. On October 23, President Obama declared an emergency, pursuant to the National Emergencies Act, with respect to the H1N1 pandemic. Specifically, the President proclaimed that because "the rapid increase in illness across the nation may overburden health care resources and ... the temporary waiver of certain standard Federal requirements may be warranted in order to enable U.S. health care facilities to implement emergency operations plans, the 2009 H1N1 influenza pandemic in the United States constitutes a national emergency." The National Emergencies Act provides the President with broad authority to waive statutory requirements, or to invoke other authorities, limited to those he specifies in an emergency declaration.