What is a close contact? Those who have one of the following contact situations with the case (observation and confirmed cases) after the onset of illness: 1, people who live, study, work or have other close contact with the case; 2, health care workers, family members or other people who have similar close contact with the case when treating, caring for or visiting the case without taking effective protective measures; 3, other patients and accompanying persons in the same ward of the case; 4, people who travel with the case in the same transportation and have close contact with the case; 5, the field investigators after investigation and assessment that the eligible personnel. At present, it is necessary to take preventive public health measures such as medical observation for close contacts, which is a responsible attitude towards public health and safety and is also a common practice in the international community. Referring to the incubation period of diseases caused by other coronaviruses, combined with information related to pneumonia cases of novel coronavirus infection and the current prevention and control of the actual situation, the period of medical observation of close contacts is set at 14 days, and the close contacts are placed under medical observation at home.