On May 27, 1993, in response to the outbreak investigation of newly recognized Hantavirus pulmonary syndrome (HPS) in the Four Corners states (New Mexico, Arizona, Utah, and Colorado), the Centers for Disease Control and Prevention established a national surveillance case definition for severe, unexplained respiratory disease to determine the extent of HPS throughout the United States. A toll-free telephone hotline number was instituted to provide updated information about unexplained respiratory illness and to serve as a passive mechanism for reporting suspected cases. Clinical information was obtained from callers reporting suspected cases, and diagnostic specimens and medical record reviews were requested from health care providers. From June 3 through December 31, 1993, the hotline received 21 443 telephone inquiries; callers identified 280 suspected cases living outside the Four Corners states with at least one specimen available for diagnostic testing. By December 31, 1993, 21 confirmed cases (age range, 14 to 58 years) residing in 11 states outside the Four Corners region had been identified. This passive surveillance system was successful in rapidly identifying the widespread sporadic geographic distribution for HPS cases throughout the United States and could serve as a model for similar emergencies. Expanding and coordinating surveillance systems for the early detection tracking, and evaluation of emerging infections is a critical component of disease prevention.
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