With regards to responding to the recent prevalence of COVID-19, Korea Centers for Disease Control and Prevention are performing defense activities to contain and prevent infection at the appropriate time, with more objective and accurate methods for monitoring patient contacts by using personal information. However, an evaluation of the effectiveness of these monitoring methods when multiple patients are involved, is necessary after the situation has been controlled. Epidemiological investigations require the collaboration of various related persons and must be conducted through a strict verification process. Furthermore, investigations must be performed using systematic processes with scientific methods and principles, and cycles of continuous evaluation and feedback to identify the etiology, extent, progression and therapy for the infectious disease and the development of public health policies.