Public health emergencies caused by infectious diseases are the greatest threat to mankind in the 21st century, and pose an even more significant threat than nuclear weapons. The first step in preparing for and responding to such public health emergencies is to conduct thorough surveillance and rapid epidemiological investigations. Especially in the case of public health emergencies, most information is not smoothly transmitted. Therefore, it is necessary to evaluate the emergency and to collect data quickly and efficiently by defining the minimum necessary data and information. In addition, these data should be analyzed and interpreted promptly, and countermeasures and strategies should be developed and utilized in preparedness and response activities. Epidemiological investigations should also be carried out promptly in accordance with the emergency situation, and in particular, if the infection source is not known, maximal measures should be taken to prevent epidemiologists from becoming infected. In order to carry out surveillance and epidemiological investigations effectively in the future in the event of a public health emergency, continuous efforts should be made to nurture professional manpower, international cooperation, and use of the latest information technology.