Five days before the symptoms of suspected cases and confirmed cases appear, or five days before the samples of asymptomatic infected persons are collected, epidemiological investigation professionals will judge them as close contacts according to epidemiological investigation results and big data information provided by relevant departments.
Novel coronavirus: "COVID-19" for short was named "20 19 coronavirus disease" by the World Health Organization, which refers to pneumonia caused by novel coronavirus infection in 20 19.