Objective:To offset the shortage of traditional large-scale population surveillance and provide early-warning signals in the early stage of the outbreak of COVID-19, people in Chongqing had carried out severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) monitoring since 2023.Methods:After COVID-19 was managed with measures against Class B infectious diseases, we selected five sewage treatment plants with automatic sample collection facilities in four districts of the main city. Two samples of sewage from each sewage treatment plant were collected every week. Then SARS-CoV-2 from these samples was concentrated by aluminum hydroxide adsorption-precipitation, detected and analyzed by multiple real-time fluorescent RT-PCR.Results:From January 16 to December 31 of 2023, a total of 496 sewage samples were monitored, of which 285 samples were positive by SARS-CoV-2 nucleic acid assay, with a total detection rate of 57.46%. The detection rate of SARS-CoV-2 in weeks 3-5, 18-21 and 40-47 was 100.00%. The daily mean nucleic acid concentration of SARS-CoV-2 in sewage peaked in the 18th week, and then began to decline, entering a low level and fluctuated in epidemic period. The variable trend of daily mean concentration of SARS-CoV-2 nucleic acid was basically consistent with daily number of SARS-CoV-2 infected patients or SARS-CoV-2 positive rate in fever clinic counted by infectious disease monitoring system.Conclusions:The detection rate of SARS-CoV-2 in sewage of Chongqing is relatively high, especially in April to May, and sewage monitoring can indirectly reflect the status of COVID-19 infection.

Objective: To explore an optimal method for granulocyte cell production from umbilical cord blood mononuclear cells. Methods: Erythrocytes were precipitated by hydroxyethyl starch. Mononuclear cells were isolated through Ficoll density gradient centrifugation. Different media, additives and cultivation model were chosen for granulocyte induction. Cell morphology was observed by microscopy, and cell phenotype was detected by flow cytometry. The CD18 expression of granulocytes was tested by immunofluorescence assay, and phagocytosis test was executed as well. Results: Compared to fetal bovine serum (FBS) treatment group, cell viability, counts and differentiation rate of granulocytes induced by X-VIVO^TM 15 combined with TPO, SCF, G-CSF but without FBS were superior. And X-VIVO^TM15 medium was better than SCGM medium at effectiveness and cost. Using two-stage mode of hematopoietic stem cell expansion followed by granulocyte induction with X-VIVO^TM15 combining TPO, SCF and G-CSF, cell proliferation was nearly 132 times at day 21. Flow cytometry showed that the differentiation was lagged in 2-stage mode than in direct induction mode, CD15 expression was (69.60± 1.06) % vs (97.73±0.39) %; Wright-Giemsa staining demonstrated mature granulocytes; immunofluorescence showed the expression of lysosomal proteins CD18. A strong phagocytic function of mature granulocytes was demonstrated by phagotrophic efficiency of (51.43±0.05) %. And granulocyte had chemotaxis ability under the role of chemotactic factor IL-8. Conclusion Optimized culture media and cultivation mode are achieved for functional granulocytes induction in vitro.