inclusion criteria: * subjects aged 18 years and above on the day of enrollment; * had recent contact with an infected person, and the time of pcr sampling from a positive infected person, or the time of first contact with a positive infected person should not exceed 72 hours; * the subjects can understand and voluntarily sign the informed consent form;

inclusion criteria: * subjects aged 18 years and above on the day of enrollment; * had recent contact with an infected person, and the time of pcr sampling from a positive infected person, or the time of first contact with a positive infected person should not exceed 72 hours; * the subjects can understand and voluntarily sign the informed consent form;

inclusion criteria: subjects aged 18 years and above on the day of enrollment; had recent contact with an infected person, and the time of pcr sampling from a positive infected person, or the time of first contact with a positive infected person should not exceed 72 hours; the subjects can understand and voluntarily sign the informed consent form;

inclusion criteria: subjects aged 18 years and above on the day of enrollment; had recent contact with an infected person, and the time of pcr sampling from a positive infected person, or the time of first contact with a positive infected person should not exceed 72 hours; the subjects can understand and voluntarily sign the informed consent form;