Red team personnel will be changed to "green code" after completing centralized isolation and home isolation medical observation management without abnormality. Yellow code personnel will go to the nearest medical institution or third-party testing institution for nucleic acid testing in time. When the test result is negative, it will turn into a green code. Those who hold a 48-hour valid negative certificate of nucleic acid detection shall be identified by the local prevention and control department and turned into a "green code" after reporting to the provincial level to perform relevant procedures.