Nanchang entry policy requires: report in advance 1 day, 48 hours of nucleic acid test certificate, 7 days of self-health monitoring, and 2 nucleic acid tests within 3 days.
The substance of nucleic acid detection is the nucleic acid of virus. Nucleic acid detection is to determine whether the patient is infected by COVID-19 by detecting whether there is nucleic acid of foreign invasive virus in respiratory tract samples, blood or feces. Therefore, once the nucleic acid is "positive", it can prove that there is a virus in the patient.