Inferring Numbers of Wild Poliovirus Excretors Using Quantitative Environmental Surveillance

Figures

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  Figure 1. Comparison of the number of plaques (log10) and DqRT-PCR Ct values obtained for poliovirus RNA extracted directly from individual concentrated EnvS samples. The Log10 of the number of plaque-forming units (PFUs) of poliovirus in a concentrated sewage (Y-axis) was compared to the Ct values obtained by DqRT-PCR Ct poliovirus RNA extracted directly from the same concentrated sewage sample (X-axis). The dashed vertical line represents the final cycle of amplification.

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  Figure 2. Addition of monovalent OPV serotypes to a sewer system and recovery of the spiked serotypes from sewage collected at EnvS site C75. Each panel in Figure 2 represents data from a separate sewage system poliovirus spike/recovery experiment. The flow diagrams for each complete spike/recovery experiment is in Supplementary Figure S1 or Figure S2. The poliovirus monovalent stocks used in the spikes and the times when they were introduced into the sewage system are indicated by blue downward pointing triangles or bars with downward pointing arrows at the top left of panels (A,B). The X-axis in each panel indicates the time in minutes after start of the peristaltic pump. The numbers in the Y-axis in the upper part of each panel represent the number of plaques recovered from EnvS samples. The red bars in the upper section of both panels indicate the number of plaques of confirmed poliovirus recovered at each individual harvest time-point. Intratypic differentiation results for these poliovirus plaques and polioviruses isolated in tube cultures from each sample are presented in the lower portion of each panel in separate rows of small rectangles, one for each serotype (PV1, PV2, and PV3).…

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  Figure 3. Comparison of (1) the number of excretors of OPV1, inferred by DqRT-PCR of OPV1 RNA extracted from EnvS samples (NexcrOPV1-inf) and (2) the number of excretors estimated from vaccination records (NexcrOPV1-est). Two methods were used to compare NExcrOPV1-inf with NExcrOPV1-est. Panel (A) represents the log10 of NExcrOPV1-est minus the log10 of NExcrOP1V-inf graphed against the mean of both log10 values. The dashed lines represent the 95% CI for the mean. Panel (B) represents a comparison of values of NExcrOP1V-inf for each EnvS catchment population calculated from DqRT-PCR with NExcrOPV1-est determined using vaccination records (X-axis and Y-axis, respectively). The solid black line in panel (B) represents the ideal curve if there was a one-to-one correlation between the log10 values estimated from the Vaccination Registry records and values inferred using the algorithm. NExcrOPV1-est and NExcrOP1V-inf were significantly correlated (two-tailed Students T test, p < 0.001). Panels (C,D) show the log10 NexcrOPV1-inf values graphed in panels (A,B) were recalculated using the calibration constant in Equation (2) and re-graphed in panels (C,D), respectively.

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  Figure 4. The inferred numbers of individuals who excreted WPV1-SoAS (NExcrWPV1-inf,) in five catchment populations in Israel during 2013 by the week the EnvS sample was obtained. In 2013, there was an asymptomatic outbreak of WPV1-SoAS. The total number of individuals who excreted WPV1-SoAS (NExcrWPV1-inf,) and the number of individuals who excreted WPV1-SoAS (NExcrWPV1-inf,) per 100,000 individuals were inferred for the catchment populations of Arara, Arad-Br-Kseife, and Rahat EnvS sites (panels (A,B), respectively). The total number of individuals who excreted WPV1-SoAS (NExcrWPV1-inf,) and the number of individuals who excreted WPV1-SoAS (NExcrWPV1-inf,) per 100,000 individuals were inferred for the catchment populations of Beersheva and Ayalon-Br-Lod EnvS sites (panels (C,D), respectively). The names of the EnvS sites indicate the names of the sewage treatment plants and should not be confused with specific cities or communities with the same name.