Fig 1.
The main analysis includes confirmed cases who were present either through residence or known dates of stay in the PL catchment area during their period of shedding (n = 12). This includes SD residents who reside within the PL area, and SD non-residents who were staying in PL during their presumed shedding period. The sensitivity analysis includes all cases with known presence in the PL catchment area during their period of presumed shedding (n = 18). In addition to the cases from the main analysis, this includes SD residents who worked or were hospitalized PL (n = 6) who were excluded from the main analysis as they did not reside in PL. Cases with no known presence in the PL catchment during their presumed shedding period were excluded regardless of SD county resident status (n = 2).
Fig 2.
Observed Wastewater Signal, Cases and their Shedding Period.
In the 308 days from September 10th 2023 to July 13th 2024 used in this analysis, there were 12 cases of HAV reported by San Diego County, represented above by points on their respective episode dates. In that same period, wastewater was sampled from the Point Loma Wastewater Treatment Facility a total of 131 times, with positive sample days being shaded orange and negative sample days in blue. A total of 48 samples tested positive for HAV nucleic acids. Each case had a 3-week long shedding period which intersected with the shedding periods of other cases, represented by the horizontal bars on each case.
Fig 3.
Distribution of Shedding and Observed Wastewater Signal.
The number of individuals shedding is shown in purple overlaid on the Observed wastewater signal during the study period. Positive sample days are shaded orange and negative sample days are blue. The number of individuals shedding at any given time ranged from 0 to 4 individuals.
Table 1.
Sensitivity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) for Detecting At Least One Case for All Wastewater Classification Methods.
Fig 4.
Sensitivity Calculated Using Wastewater signal reclassified based on 5-sample trimmed centered average.
Sensitivity increases as the number of individuals shedding increases across shedding periods (Blue dashed line: 1 week before and 1 week after symptom onset; Red solid line: 2 weeks before and 1 week after symptom onset; Orange dotted line: 1 week before and 4 weeks after symptom onset; Green dash-dotted line: 2 weeks before and 4 weeks after symptom onset). Sensitivity for identification of at least one case is higher for shorter shedding periods.