Close contacts of novel coronavirus are those who have one of the following contact situations with suspected cases, confirmed cases and positive testers, but have not taken effective protection: 1, living, studying, working together, or other people who have close contact, such as working in close proximity; 2, medical staff, family members or other people who have similar close contact with the treatment, care or visitation of cases, such as visiting patients in a confined environment; 3 3, travel on the same transport and have close contact with personnel, including caregivers on the transport; fellow travelers; other passengers and crew members who have close contact with suspected cases, confirmed cases and positive testers; 4, other cases.