SARS is a severe viral infection that is sometimes fatal. The disease first emerged in China in 2002 and then spread through Asia to 26 countries around the world. Although national governments are responsible for responding to infectious disease outbreaks such as SARS, WHO plays an important role in coordinating the response to the global spread of infectious diseases and assisting countries with their public health response to outbreaks. The U.S. government plays a role during international outbreaks in assisting WHO and affected countries and protecting U.S. citizens and interests at home and abroad. The virus that causes SARS is a member of a family of viruses known as coronaviruses, which are thought to cause about 10 percent to 15 percent of common colds. Within 2 to 10 days after infection with the SARS virus, an individual may begin to develop symptoms—including cough, fever, and body aches—that are difficult to distinguish from those of other respiratory illnesses. The primary mode of transmission appears to be direct or indirect contact with respiratory secretions or contaminated objects. Another feature of the disease is the occurrence of “superspreading events,” where evidence suggests that the disease is transmitted at a high rate due to a combination of patient, environmental, and other factors. According to WHO, the global case fatality rate for SARS is approximately 11 percent and may be more than 50 percent for individuals over age 65. The management of a SARS outbreak relies on the use of established public health measures for the control of infectious diseases—including case identification and contact tracing, transmission control, and exposure management, defined as follows: Case identification and contact tracing: defining what symptoms, laboratory results, and medical histories constitute a positive case in a patient and tracing and tracking individuals who may have been exposed to these patients. Transmission control: controlling the transmission of disease- producing microorganisms through use of proper hand hygiene and personal protective equipment, such as masks, gowns, and gloves. Exposure management: separating infected and noninfected individuals. Quarantine is a type of exposure management that refers to the separation or restriction of movement of individuals who are not yet ill but were exposed to an infectious agent and are potentially infectious. The emergence of SARS in China can be traced to reports of cases of atypical pneumonia in several cities throughout Guangdong Province in November 2002. (See fig. 1 for a timeline of the emergence of SARS cases and WHO and U.S. government actions.) Because atypical pneumonia is not unusual in this region and the cases did not appear to be connected, many of these early cases were not recognized as a new disease. However, physicians were alarmed because of the unusual number of health care workers who became severely ill after treating patients with a diagnosis of atypical pneumonia. The international outbreak began in February 2003 when an infected physician who had treated some of these patients in China traveled to Hong Kong and stayed at a local hotel. Some individuals who visited the hotel acquired the infection and subsequently traveled to Vietnam, Singapore, and Toronto and seeded secondary outbreaks. Throughout spring 2003, the number of cases continued to spread through Asia to 26 countries around the world, and at its peak—in early May— hundreds of new SARS cases were reported every week. (See app. I for a map of total SARS cases and deaths.) In July 2003, WHO announced that the outbreak had been contained. (See app. II for a detailed chronology of the SARS outbreak.) Although national governments bear primary responsibility for disease surveillance and response, WHO, an agency of the United Nations, plays a central role in global infectious disease control. WHO provides support, information, and recommendations to governments and the international community during outbreaks of infectious disease that threaten global health or trade. The International Health Regulations outline WHO’s authority and member states’ obligations in preventing the global spread of infectious diseases. Adopted in 1951 and last modified in 1981, the International Health Regulations are designed to ensure maximum security against the international spread of diseases with a minimum of interference with world traffic (that is, trade and travel). The current regulations require that member states report the incidence of three diseases within their borders—cholera, plague, and yellow fever—and WHO can investigate an outbreak only after receiving the consent of the government involved. Efforts to revise the regulations began in 1995, and the revised regulations are scheduled to be ready for submission to the World Health Assembly, the governing body of WHO, in May 2005. While the International Health Regulations provide the legal framework for global infectious disease control, WHO’s Global Outbreak Alert and Response Network (GOARN), established in April 2000, is the primary mechanism by which WHO mobilizes technical resources for the investigation of, and response to, disease outbreaks of international importance. Because WHO does not have the human and financial resources to respond to all disease outbreaks, GOARN relies on the resources of its partners, including scientific and public health institutions in member states, surveillance and laboratory networks (e.g., WHO’s Global Influenza Surveillance Network), other U.N. organizations, the International Committee of the Red Cross, and international humanitarian nongovernmental organizations. WHO collects intelligence about outbreaks through various sources, including formal reports from governments and WHO officials in the field as well as informal reports from the media and the Internet. When WHO receives a formal request for assistance from a national government, it responds primarily through GOARN. GOARN’s key response objectives are to ensure that appropriate technical assistance rapidly reaches affected areas during an outbreak and to strengthen public health response capacity within countries for future outbreaks. Its response activities may include providing technical advice or support (e.g., public health experts and laboratory services), logistical aid (e.g., supplies and vaccines), and financial assistance (e.g., emergency funds). In addition to the support provided through GOARN, technical assistance and deployments are also arranged through WHO’s regional offices. Two departments of the U.S. government, the Department of Health and Human Services (HHS) and State, play major roles in responding to infectious disease outbreaks overseas. Within HHS, the Office of Global Health Affairs and CDC work closely with WHO and foreign governments in response efforts. CDC also works with other federal agencies, state and local health departments, and the travel industry to limit the introduction of communicable diseases into the United States. State’s roles include protecting U.S. government employees working overseas and disseminating information about situations that may pose a threat to U.S. citizens living and traveling abroad. In addition, State may coordinate the provision of technical assistance by various U.S. government agencies and use its diplomatic contacts to engage foreign governments on policy issues related to infectious disease response. In recent years, Asia has become increasingly vulnerable to emerging infectious disease outbreaks, and governments have had to deal with diseases such as avian influenza and dengue fever. In China, Hong Kong, and Taiwan, such infectious disease outbreaks are managed through the public health authorities of these governments: China: The Ministry of Health maintains lead authority over health policy at the national level, although provincial governments exercise significant authority over local health matters. In January 2002, the national Center for Disease Control and Prevention was established, along with centers at the provincial and local levels, and charged with matters ranging from infectious disease control to chronic disease management. Hong Kong: The Health, Welfare, and Food Bureau has overall policy responsibility for health care delivery and other human services in Hong Kong. Within the bureau, the Department of Health and its Disease Prevention and Control Division, which was established in July 2000, are responsible for formulating strategies and implementing measures in the surveillance, prevention, and control of communicable diseases. The Hospital Authority is responsible for the management of 43 public hospitals in Hong Kong. Taiwan: The Department of Health is responsible for national health matters and for guiding, supervising, and coordinating local health bureaus. A division of the department, the Taiwan Center for Disease Control, was established in 1999 and consolidated the disease prevention work of several national public health agencies involved in infectious disease control. WHO’s actions to respond to the SARS outbreak were extensive, but its response was delayed by an initial lack of cooperation from officials in China and challenged by limited resources. WHO’s actions included direct technical assistance to affected areas and broad international actions such as alerting the international community about this serious disease and issuing information, guidance, and recommendations to government officials, health professionals, the general public, and the media. (See fig. 1 for key WHO actions during the SARS outbreak.) However, an initial lack of cooperation on the part of China limited WHO’s access to information about the outbreak, and WHO had to stretch its resources for infectious disease control to capacity. WHO’s response to SARS was coordinated jointly by WHO headquarters and its Western Pacific Regional Office (WPRO). At headquarters, WHO activated its GOARN. Although GOARN had been used before to respond to isolated outbreaks of Ebola, meningitis, viral hemorrhagic fever, and cholera in African countries and elsewhere, the SARS outbreak was the first time the network was activated on such a large scale for an international outbreak of an unknown emerging infectious disease. There were two primary aspects to WHO’s activities during the SARS outbreak: One was the direct deployment of public health specialists from around the world to affected Asian governments to provide technical assistance; the other was the formation of three virtual networks of laboratory specialists, clinicians, and epidemiologists who pooled their knowledge, expertise, and resources to collect and develop the information WHO needed to issue its guidance and communications about SARS. Under GOARN’s auspices, WHO rapidly deployed 115 specialists from 26 institutions in 17 countries to provide direct technical assistance to SARS- affected areas. WPRO also facilitated the deployment of an additional 80 public health specialists to SARS-affected areas. Asian governments identified their needs for technical assistance—consisting primarily of more senior, experienced staff—and then WHO issued a request for staff from its partners. WHO officials at headquarters and at WPRO worked jointly to quickly process contracts and send teams into the field within 48 hours of the request. The work of the teams varied, depending on local need.