Interactive City-wide Sewage Surveillance Program for COVID-19 in Hong Kong

City-wide Sewage Surveillance Program

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Programme Overview
Field Sampling Strategy
Areas of Innovation
Achievements
Reference Materials

Programme Overview

In response to the COVID-19 pandemic, the HKSAR Government established an inter-departmental working team comprising over 400 people with different specialties to launch the Territory-wide Interactive Sewage Surveillance Programme for Assisting Real-time COVID-19 Pandemic Control in Hong Kong, an innovative, tiered and cost-effective approach that can complement conventional epidemiological surveillance. The Environmental Protection Department (EPD) mastered the program implementation with key responsibilities to devise sampling strategy, analyze data and execute district-based intervention actions while the Drainage Services Department (DSD) took lead to plan and carry out sewage sampling. The EPD and DSD collaborated with the cross-disciplinary team of The University of Hong Kong (HKU) to develop the sewage testing methodologies and the Department of Health (DH) rendered professional support in offering epidemiology advices.

Objectives of Sewage Surveillance

	Provide early warning signals of COVID-19 outbreak in the community
	Monitor infection clusters for intervention actions
	Track the epidemic development in the community

The sewage testing results provided robust scientific basis for the implementation of risk-based district-level intervention actions to identify hidden COVID-19 cases for timely isolation, complementing the general non-pharmaceutical intervention measures enacted across the city.

Field Sampling Strategy

Hong Kong has a comprehensive public sewerage system with centralised sewage treatment works covering 93% of its population. About 95% of the sewage collected is conveyed to six large sewage treatment works with a total volume of 100,000 – 2,000,000 m³/day. This centralised system has rendered sewage surveillance at sewage treatment works alone insufficient. The Government adopted a city-wide sewerage network-based sewage surveillance programme which could better capture the spatial distribution of SARS-CoV-2 signals across the territory.

Through sewerage network analysis, representative manholes were identified as sampling sites (i.e. stationary sites) for sewage collection to detect the presence of COVID-19 virus. Site investigations and trials were then conducted to ascertain sampling suitability. Each stationary site represented an average population of 40,000 (range 10,000 – 260,000), a size manageable for the Government to detect positive signals and conduct upstream tracing, if deemed necessary, for identifying hidden cases. The number of stationary sites was progressively increased from 26 during the initial pilot sewage surveillance in October 2020, to 64 for larger coverage in early 2021, and then to 154 during the 5^th wave of COVID-19 in early 2022. The population coverage was also increased from 2 to 4 million, and finally to 6 million, equivalent to 80% of Hong Kong’s population. The number of stationary sites was slightly reduced from 154 to 120 through sampling plan optimization starting from mid Jan 2023 in view of the stable COVID-19 pandemic situation, achieving adequate resource allocation without compromising the high percentage of population coverage. The sampling frequency was increased from a 5-day cycle (i.e. all stationary sites were sampled once every 5 days) in early 2021 to a 2-day cycle during the 5^th wave to capture the short incubation period (about 3 days) of the prevailing Omicron variant.

污水井自動採樣器的設置

Setup of in-manhole automatic sampler

Sampling

Laboratory Analysis

Areas of Innovation

✓ The first city-wide full-scale application of sewage test to support COVID-19 control strategies including Restriction Testing Declaration (RTD), Compulsory Testing Notices (CTN) and distribution of Rapid Antigen Test (RAT) kits.

RTD

Restriction Testing Declaration (RTD)

CTN

Compulsory Testing Notices (CTN)

RAT

Distribution of Rapid Antigen Test (RAT) kits

✓ A smart deployment of HK’s extensively-covered and fully-documented sewerage network.

✓ Synergy among government, academics and private sectors to produce continuous epidemic data with high reliability in protecting public health.

✓ Use of new technologies including GIS, Business Intelligence and Big data analysis to handle mass quantity of daily information to enable immediate follow up actions.

✓ World leading position in the monitoring of COVID-19 virus variants.

新冠疫情污水監測網上地理信息系統平台

COVID-19 Sewage Surveillance Web-GIS platform

Achievements

渠務署和環保署團隊獲行政長官嘉許

DSD & EPD Teams receiving commendations

公務員優質服務獎勵計劃 – 卓越的合作夥伴關係

Meritorious Award in Outstanding Civil Service Award – Excellence in Partnership

2023年香港工程師學會年度大獎

The HKIE Grand Award 2023 :

Grand Prize - An Invention

Merits – An Innovative Application

2024 International Water Association (IWA) Project Innovation Awards

Gold Award (Performance Improvement and Operational Solutions)

Where can I find Sewage Surveillance testing results?
Results can be found on the following website:
https://www.chp.gov.hk/en/resources/29/100148.html

Reference Materials
City-wide Sewage Surveillance Program introduction video

Media Coverage