The cause of the epidemic. As of September 29, 2022, according to the epidemic prevention requirements of Shenzhen, Guangdong Province, Shenzhen, Guangdong Province belongs to a medium-risk area, so the bus No.306 from Shenzhen Cuifeng Haoyuan Terminal to the railway station stopped. In the middle-risk area, the control measures of "people don't leave the area, taking things at the wrong peak" are implemented. Three consecutive nucleic acid tests were carried out in the first three days after the implementation of closed control, and the frequency of subsequent tests was determined according to the test results.