Passive sampling to scale wastewater surveillance of infectious disease: Lessons learned from COVID-19

Much of what is known and theorized concerning passive sampling techniques has been developed considering chemical analytes. Yet, historically, biological analytes, such as Salmonella typhi, have been collected from wastewater via passive sampling with Moore swabs. In response to the COVID-19 pandemic, passive sampling is re-emerging as a promising technique to monitor SARS-CoV-2 RNA in wastewater. Method comparisons and disease surveillance using composite, grab, and passive sampling for SARS-CoV-2 RNA detection have found passive sampling with a variety of materials routinely produced qualitative results superior to grab samples and useful for sub-sewershed surveillance of COVID-19. Among individual studies, SARS-CoV-2 RNA concentrations derived from passive samplers demonstrated heterogeneous correlation with concentrations from paired composite samples ranging from weak (R2= 0.27, 0.31) to moderate (R2= 0.59) to strong (R2= 0.76). Among passive sampler materials, electronegative membranes have shown great promise with linear uptake of SARS-CoV-2 RNA observed for exposure durations of 24 to 48 h and in several cases RNA positivity on par with composite samples. Continuing development of passive sampling methods for the surveillance of infectious diseases via diverse forms of fecal waste should focus on optimizing sampler materials for the efficient uptake and recovery of biological analytes, kit-free extraction, and resourceefficient testing methods capable of rapidly producing qualitative or quantitative data. With such refinements passive sampling could prove to be a fundamental tool for scaling wastewater surveillance of infectious disease, especially among the 1.8 billion persons living in low-resource settings served by non-traditional wastewater collection infrastructure.

Automated summary

Passive sampling is a promising technique for monitoring SARS-CoV-2 RNA in wastewater during the COVID-19 pandemic. It has been found to produce qualitative results superior to grab samples and useful for sub-sewershed surveillance of COVID-19. However, there is heterogeneity in the correlation between passive samplers and composite samples for SARS-CoV-2 RNA concentrations. Electronegative membranes show great promise as passive sampler materials. Further development of passive sampling methods should focus on optimizing sampler materials, kit-free extraction, and resource-efficient testing methods.