SARS-CoV-2 titers in wastewater are higher than expected from clinically confirmed cases

Fuqing Wu; Amy Xiao; Jianbo Zhang; Xiaoqiong Gu; Wei Lin Lee; Kathryn Kauffman; William Hanage; Mariana Matus; Newsha Ghaeli; Noriko Endo; Claire Duvallet; Katya Moniz; Timothy Erickson; Peter Chai; Janelle Thompson; Eric Alm

is the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.04.05.20051540 doi: medRxiv preprint Discussion. These data suggest an order of magnitude estimate of approximately 100 viral particles per mL of sewage, but what conclusions can be drawn about disease prevalence? First, we note that any rigorous conclusions depend on a number of factors that are unknown, and thus additional experiments will be required to calibrate these numbers. Nonetheless, we can estimate an abundance based on the lowest observed values across these samples of ~10 copies/mL. If we assume typical stool sizes of 200g, diluted into an average volume of 1.36*10 9 L, and a population of 2.3*10 6 individuals each producing one stool per day, and we further assume that there is no loss of viral RNA in sewer lines and that excreted viruses are fully suspended in sewage, then we expect the viral titer in feces to be about 3000 times higher than that in sampled raw sewage, or about 30,000 particles per mL.