New crown 15 days has not turned negative relatively serious, may be related to viral load, autoimmune, re-positive and other factors. 1. Viral load, may be their own body’s viral load is relatively large, after isolation and observation or treatment of viral load decline is not obvious, then there will be nucleic acid test has not been turned negative situation, relatively serious. 2. Autoimmunity, for asymptomatic and mildly infected people, if their own immunity is poor, unable to completely control the virus in their bodies through intensive isolation, similar situations may occur, more serious than other infected people. 3. Repeat positive, may have turned negative during isolation or treatment, but in a short period of time the infection reappears, then the nucleic acid test is positive. Patients are advised to cooperate actively with isolation and treatment.