Objective   To analyze epidemiological and clinical characteristics of retest positive cases infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Chengdu city, Sichuan province and to provide evidences for the prevention and control of coronavirus disease 2019 (COVID-19).

  Methods  Relevant data on 147 SARS-CoV-2 nucleic acid retest positive cases were retrospectively collected from follow-up surveys conducted 2 and 4 weeks after hospital discharge among 977 COVID-19 patients in Chengdu city as of June 15, 2021. The epidemiological and clinical characteristics of the retest positive cases during hospitalization and at the retest were described.

  Results  The retest positive rate of SARS-CoV-2 nucleic acid was 15.05% and there was no significant type difference in the retest positive rate for a total of 440 various biological specimens from the cases (all P > 0.05). The chest images showed progressive lesions in 12 retest positive cases and another 12 cases presented clinical symptoms of COVID-19. Among 180 surface swab specimens sampled in living environment of the retest positive cases, two were positive for SARS-CoV-2 nucleic acid test. For all the retest positive cases, the average interval from discharge to the time of retest positive was 16.95 days and the average detoxification period was 56.58 days. The cases′ detection results of lymphocyte count, D-dimer, serum ferritin, creatine kinase isoenzymes at the time of retest positive and duration of hospitalization were significantly different from those at the time before the retest positivity (P < 0.05 for all).

  Conclusion  Retest positive for SARS-CoV-2 nucleic acid exists and could be detected in various biological specimens among discharged COVID-19 cases. Detections of multiple specimens can facilitate the identification of the rest positive cases.