Feasibility of wastewater-based epidemiology on COVID-19 in 3 cities of Japan and development of an early warning indicator of disease outbreak

Abstract

 This study aimed to evaluate feasibility of wastewater-based epidemiology in Japan by long-term monitoring of SARS-CoV-2 RNA in wastewater at municipal wastewater treatment plants in 3 cities of Japan. The viral titers in wastewater exhibited significant correlations with clinically reported cases of COVID-19 in all the 3 cities during the 7th wave of outbreak. A viral loading in wastewater, which is normalized the viral titer by multiplying the detected viral concentration with daily quantity of influent wastewater, exhibited better correlations than viral concentrations. Importantly, surges of viral titers in wastewater were found when big sport events were organized during the 6th wave in Ota city. This suggests that wastewater-based epidemiology is effective to detect visit of infected people from outside of the city. In this study a W/C ratio, which is calculated as a ratio of viral titers in wastewater to the number of clinically reported cases was shown to have the potential to forecast probability of increase in clinically reported cases in the following week.