Isolated for many days will still have a new crown positive may be the new crown virus has a long incubation period, the detection reagent sensitivity is not enough, sampling is not standardized and so on. 1. long incubation period: the new crown virus has a certain incubation period, the incubation period of the patient did not appear special symptoms, medical personnel in the screening did not screen out, isolation for many days, the virus spreads, the corresponding symptoms appear, resulting in a positive test of the new crown. 2. Insufficient sensitivity of the test reagent: the patient is in the early stage of disease development, the viral load in the body is lower than the detection limit, and there is not a sufficient amount of virus in the collected specimen to be used for the test. 3. sampling is not standardized: if the sampling site and sampling operation is not standardized, then the possibility of picking a positive specimen will be greater, or the laboratory does not strictly follow the quality management of gene amplification test laboratory. Such as specimens or nucleic acid purification process of amplification reaction inhibitors, amplifier hole temperature differences and nucleic acid extraction in the random error, can cause isolation for many days will still have a new crown positive phenomenon. If the phenomenon of new crown positive even after many days of isolation occurs, it should be promptly examined in the hospital to clarify the cause of treatment.