Wastewater Surveillance Provides Spatiotemporal Dynamics of SARS-CoV-2 Infections in a Megacity: Hong Kong's Case Study

Background: During the COVID-19 pandemic, obtaining timely and accurate pandemic trends is essential for carrying out effective control policies and targeted resource allocation. Wastewater surveillance can take advantage of its wide coverage, convenient sampling, and high monitoring frequency to capture a city-wide pandemic trend independently from clinical surveillance.Methods: We conducted a 9-month SARS-CoV-2 wastewater surveillance from 12 wastewater treatment plants (WWTPs) to monitor infection dynamics from February 14, 2022, to November 1, 2022. Totally, 2887 wastewater samples were concentrated by polyethylene glycol (PEG) precipitation and quantified by RT-qPCR to determine SARS-CoV-2 virus concentration. In addition, daily number of reported cases from Centre for Health Protection (CHP) database, daily point-prevalence from online dashboard from independent community rapid antigen test (RAT) surveillance and city-wide sero-surveillance dataset were collected to compare with the prevalence/incidence rates estimated from wastewater measurements.Findings: The wastewater virus concentration correlated with daily number of reported cases and reached the peak three days earlier for both the first and second peaks. Two different methods, based on virus shedding load and reported cases in low infection rate period, were established to estimate the prevalence/incidence rates from wastewater measurements, and the results were comparable to the community RAT surveillance and sero-surveillance but higher than the cases reported by CHP. In addition, the effective reproductive number (Rt) was estimated from wastewater surveillance to reflect the transmission dynamics at both the city-wide and regional levels.Interpretation: Our findings demonstrate large-scale intensive wastewater surveillance from WWTPs provides cost-effective and timely public health information, especially when the clinical surveillance is inadequate and costly during the pandemic outbreak. This approach also helps reveal the spatiotemporal pandemic dynamic at higher spatiotemporal resolutions for targeted interventions.Funding: Health and Medical Research Fund (HMRF) (COVID1903015), The Government of the Hong Kong Special Administrative Region (SAR), China.Declaration of Interest: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.