污水中新型冠状病毒监测技术的进展与启示

Advances and implications of wastewater surveillance for SARS-CoV-2

污水流行病学的概念最早于2001年提出[1],最初是通过追踪污水中多种与人群健康和行为相关的化学与生物标记物,对使用毒品与非法药物的群体进行精准溯源[2],或是预警、跟踪和遏制传染病的暴发及其在社区中的传播[3].其中一个典型的应用实例是2013年以色列在常规污水监测中发现了被认为已经根除的脊髓灰质炎病毒,随即据此展开大规模疫苗接种从而成功避免了小儿麻痹症在当地的再次暴发.

Wastewater-based epidemiology(WBE)is a tool for monitoring the trend and spread of infectious diseases in populations.The COVID-19 pandemic has led to a surge in interest in studying WBE since it can offer a non-invasive and cost-effective way for monitoring the virus at population level.This paper discusses the principles and practices of WBE in the context of COVID-19,with a focus on its applications in Hong Kong.WBE relies on the detection of viral RNA in sewage samples,which can indicate the presence and amount of the virus in a surveyed population.The detection process involves three key steps,including sewage concentration,nucleic acid extraction,and quantitative polymerase chain reaction(qPCR)amplification of target virus sequences.Quality control measures such as positive and negative controls are crucial for generating accurate and reliable testing results.In Hong Kong,a comprehensive WBE system has been established from the ground up in 2020,which now covers 10 large sewage treatment plants,154 community surveillance sites,and multiple ad hoc sites across residential areas.The adopted sampling frequency and methods could vary according to the type of sampling site and the stage of an outbreak.Composite sewage samples are collected using automatic samplers and analyzed using standardized methods.The data generated from the WBE system is used for providing early warning and epidemiological assessment,as well as guiding public health interventions.However,the interpretation of WBE results requires careful consideration of various factors that can affect the accuracy and sensitivity of the method.These factors include the amount,frequency,and probability of viral shedding in infected individuals,variations in viral shedding over time and across different virus variants,the decay of viral particles in sewage along the sewer system and testing procedure,and the detection limit of the adopted testing method.In addition,the presence of false negative results due to randomness in sampling and fecal shedding is a significant challenge in interpretating WBE results.Therefore,it is essential to include appropriate quality control measures,use optimized sampling strategies,and validate the sewage testing data with clinical and epidemiological evidence.Despite these challenges,the experience of Hong Kong shows that WBE could provide valuable information for monitoring and responding to COVID-19 outbreaks.The WBE system in Hong Kong has been shown to be able to provide early signals of viral transmission,track the development trend of the epidemic,and locate high-risk areas for targeted public health interventions.The success of the Hong Kong WBE system highlights the importance of a comprehensive surveillance system and adaptive methods used in WBE,which requires ongoing evaluation and data analysis.WBE is a promising tool for surveying infectious diseases in populations,and its application in COVID-19 surveillance worldwide has demonstrated its great potential.However,the interpretation of WBE results requires careful considerations of various factors,such as the method’s sensitivity and specificity may vary across populations and stages of an outbreak.Therefore,the establishment of a comprehensive and adaptive WBE system that integrates epidemiological,clinical,and environmental data is important for achieving the full potential of this tool in infectious disease surveillance and control.