Wastewater monitoring in support of health surveillance of the COVID-19 pandemic

Surveillance of infectious disease pandemics is traditionally carried out by the inventory of individual clinical cases, mortality, and biological testing. Collective monitoring through the analysis of biomarkers in wastewater is a new complementary approach developed due to progress in analytical chemistry. It supports epidemiological studies for the estimation of the prevalence of viral infectious diseases within communities connected to the same wastewater sewage network. In the context of the COVID-19 pandemic, this type of approach has developed widely and rapidly around the world, due to its anticipated benefits. The article builds on early work published since January 2020 in a rapidly evolving literature. It shows that the method has limitations related in particular to the sampling strategy, analytical matrix effects, interlaboratory variability of results, and also uncertainties about individual viral excretion in feces. In almost all cases, it uses genomic detection of SARS-CoV-2 virus by quantitative PCR and is therefore unable to characterize its infectivity. The results showed a relatively good relation between genome concentrations in wastewater and numbers of confirmed cases. The virus detections seemed to appear a few days before the changes observed on the basis of the clinical and test screenings and can alert the health authorities to the geographical progression of an expected epidemic or to anticipate their reaction in the event of a new spike of the current epidemic. Knowledge of the evolutionary trends of wastewater virus contamination in cities, or even in city districts, also makes it possible to better target geographically and over time the public health management actions intended to prevent the circulation of the virus in the population served by their sewerage systems. In connection with health surveillance, the method is intended to contribute to the development of epidemiological models to predict the evolution of the pandemic at the local level. It is expected to develop into a permanent surveillance network over the territories, providing early, real-time epidemiological indications. Wastewater monitoring could also feed a pool of control samples to determine retrospectively when a new outbreak of viral infection has entered a territory.