Abstract:
Objective To investigate the dynamic distribution characteristics of norovirus (NoV) in the wastewater in Chaoyang district, Beijing, China, address the deficiency of conventional population monitoring, and provide basic data for quantitative studies on the correlation between NoV in wastewater and NoV infection in the population as well as studies predicting infection in the population through preliminary analysis of the detection, nucleic acid concentration, and accuracy of model fitting of NoV in wastewater in this area.
Methods Wastewater samples from eight wastewater treatment plants (WWTPs) in Chaoyang district were collected from June 2023 to June 2024. The NoV in wastewater was enriched and concentrated using the magnetic bead method and was measured for the GI/GII nucleic acid using quantitative reverse transcription polymerase chain reaction (qRT-PCR). The NoV GI/GII positive detection rate and copy number (copies/mL) were calculated and analyzed. An autoregressive integrated moving average (ARIMA) model was constructed using NoV GII copy numbers from Week 22 of 2023 to Week 21 of 2024, and the model was fitted and validated using monitoring data from Week 22 of 2024 to Week 26 of 2024.
Results From June 2023 to June 2024, a total of 904 wastewater samples were collected, and the overall positive detection rates of NoV GI and GII were 93.92% (849/904) and 95.35% (862/904), respectively (χ2=1.84, P>0.05), with the dual-positive rate for types GI and GII being 92.37% (835/904). The median copy numbers of GI and GII were 269.499 (108.607, 588.880) and 323.017 (91.655, 713.353) copies/mL, respectively(Z=2.17, P=0.030). There were no significant differences between the positive detection rate and copy number of NoV GI and GII across the eight WWTPs, with a consistent trend in the prevalence of NoV GII copy number across the WWTPs (F=2.82, P=0.093), while there was a significant difference in the trend in the prevalence of type GI copy number (F=7.25, P=0.007). There were significant differences in seasonal distributions of NoV copy numbers of GI and GII (P < 0.05), with the highest monthly average copy number in the spring (GI: 603.607 copies/mL, GII: 1 114.240 copies/mL). The optimal fitting model for the GII copy number of NoV in wastewater was ARIMA (2, 0, 3) (smooth R2=0.606, BIC=10.786), with a mean relative errors of the fitted copy numbers of ≤17.15%, a root mean square error of 171.507, and a mean absolute percentage error of 82.557%.
Conclusion NoV and/or its nucleic acid fragments were consistently detected in the wastewater in Chaoyang district, Beijing, throughout the year from 2023 to 2024. Therefore, it is necessary to pay attention to the potential epidemiological risks in the trough. It is recommended to continuously monitor the situation, accumulate relevant data, and timely calibrate the fitting of the ARIMA model to improve its accuracy and sensitivity. It is worth attempting to predict disease and monitor prevalence through wastewater monitoring.
下载: