No abstract

Presence of SARS-coronavirus-2 (SARS-CoV-2) in wastewater sample has been documented in several countries. Wastewater-based epidemiology (WBE) is potentially effective for early warning of COVID-19 outbreak. The purpose of this study was to verify the detection limit of WBE for COVID-19. In total, 27 influent wastewater samples were collected from four wastewater treatment plants in Ishikawa and Toyama prefectures in Japan. During the study period, numbers of the confirmed COVID-19 cases in these prefectures increased from almost 0 to around 20 per 100,000 peoples. SARS-CoV-2 RNA in the samples were identified by several PCR-based assays. Among the 27 samples, 7 were positive for SARS-CoV-2 by at least one out of the three quantitative RT-PCR assays. These samples were also positive by RT-nested PCR assays. The detection frequency became higher when the number of total confirmed SARS-CoV-2 cases in 100,000 peoples became above 10 in each prefecture. However, SARS-CoV-2 could also be detected with a low frequency when the number was below 1.0. Considering that the number of the confirmed cases does not necessarily reflect the actual prevalence of the infection at the time point, data on the relationship between the number of infection cases and concentration in wastewater needs to be accumulated further.

No abstract

To date, several microbes have been proposed as potential source-specific indicators of fecal pollution. 16S ribosomal RNA gene markers of the Bacteroidales species are the most widely applied due to their predominance in the water environment and source specificity. F-specific bacteriophage (FPH) subgroups, especially FRNA phage genogroups, are also known as potential source-specific viral indicators. Since they can be quantified by both culture-based and molecular assays, they may also be useful as indicators for estimating viral inactivation in the environment. Pepper mild mottle virus (PMMoV) and crAssphage, which are frequently present in human feces, are also potentially useful as human-specific indicators of viral pollution. This study aimed to evaluate the applicability of FPH subgroups, PMMoV, and crAssphage as indicators of source-specific fecal contamination and viral inactivation using 108 surface water samples collected at five sites affected by municipal and pig farm wastewater. The host specificity of the FPH subgroups, PMMoV, and crAssphage was evaluated by principal component analysis (PCA) along with other microbial indicators, such as 16S ribosomal RNA gene markers of the Bacteroidales species. The viabilities (infectivity indices) of FRNA phage genogroups were estimated by comparing their numbers determined by infectivity-based and molecular assays. The PCA explained 58.2% of the total information and classified microbes into three groups: those considered to be associated with pig and human fecal contamination and others. Infective and gene of genogroup IV (GIV)-FRNA phage were assumed to be specific to pig fecal contamination, while the genes of GII-FRNA phage and crAssphage were identified to be specific to human fecal contamination. However, PMMoV, infective GI-FRNA phage, and FDNA phage were suggested to not be specific to human or pig fecal contamination. FRNA phage genogroups, especially the GIV-FRNA phage, were highly inactivated in the warm months in Japan (i.e., July to November). Comparing the infectivity index of several FRNA phage genogroups or other viruses may provide further insight into viral inactivation in the natural environment and by water treatments.