Infectious diseases are important, evolving, and complex public health problems. They are the leading cause of death worldwide. However, the United States has grown complacent regarding infectious diseases due to improvements in sanitation and effective antibiotics and vaccines. A 1992 report by the Institute of Medicine (IOM) on emerging infections in the United States and their potential threat was discussed emphasizing the complacency, threats of infectious diseases, factors contributing to disease emergence and reemergence, and the need for increased vigilance, disease detection, and response capacity. It is of significant importance that major challenges posed by emerging infectious diseases outbreaks receive and require timely epidemiologic investigations, use of sophisticated laboratory techniques, and effective communication of results and recommendations for prevention. An integrated approach involving epidemiologic, laboratory, behavioral, and information sciences was seen as critical to the prevention and control of infectious diseases. The best defense against any disease outbreak (naturally occurring or intentionally caused) is a strong and flexible public health infrastructure.