A Powerful Sewage Surveillance System
to Help Fight COVID-19
Do you know that effective sewage testing could help combat COVID-19?
The sewage test results are a basis for statutory public health action in identifying buildings and places for compulsory testing operations to discover infected individuals in Hong Kong. Since December 2020, the sewage monitoring technology developed by the HKU multidisciplinary team led by Professor Tong Zhang of the Department of Civil Engineering has been incorporated as one of the key components of the control strategy for fighting against COVID-19 in Hong Kong.
At the moment, the systematic routine sewage monitoring programme of the Environmental Protection Department (EPD) and the Drainage Services Department (DSD) covers 112 regular sampling sites in Hong Kong, providing early warning signals of COVID-19 re-emergence for over five million people. Thanks to that, we are able to quickly locate and isolate infected people before the virus could do more damage.
Meanwhile, in light of the emerging highly transmissible SARS-CoV-2 variants worldwide, the team has developed a helpful method for identification and quantification of different SARS-CoV-2 variants in sewage using allele-specific RT-qPCR based technology.
Allele-specific RT-qPCR technology VS Virus genome sequencing method
“EPD and DSD’s routine sewage monitoring programme is a powerful radar,” said Professor Zhang.
With primer-probe sets designed by the team, specific mutation sites of different types of variants could be detected and identified with a very high level of accuracy.
In comparison to the genomic sequencing, this method excels in the following ways:
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Has a much shorter turn-over time (only needs a few hours)
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Serve as a rapid screening of different variants for quick follow-up actions
As such, relevant authorities can respond more quickly to the situation and minimise the risk of large-area infection. Professor Zhang reminded us, however, that “the genome sequencing of patients is still needed for transmission analysis in the later stage”. Nonetheless, he is much encouraged by the benefits the new sewage testing methods brought about.
Why is the Allele-specific RT-qPCR technology better?
Remember the first Delta variant found in Tai Po on June 21, 2021? This was discovered by the Allele-specific RT-qPCR technology. The whole process of identification to public announcement was carried out with astonishing efficiency.
Within half a day, the team was able to detect positive signals of L452R along with two other mutations of the Delta variant, then reported it to the Government -- “HKU's test results about the mutations using Allele-specific RT-qPCR indicated that it is Delta (Indian) variant with a very high probability.” The Government then issued the Compulsory Testing Notice (due to sewage positive signal) in the afternoon next day (June 23), followed by the Restriction-Testing Declaration (due to the “preliminary positive” case) in the evening of the same day.
This incident sheds light to the significant role sewage testing plays in serving as the first alarm to the introduction of the Delta variant in local community sewage.
Sewage may tell the health of a city, and we are learning how to listen to it.Professor Zhang
While we often look at life expectancy and crude death rate to determine the healthiness of a city, the sewage could be very telling of the city’s vitality.
The current practice of the sewage surveillance in Hong Kong has clearly demonstrated its crucial role in the fight against COVID by providing early warning signals of the outbreak of COVID-19. They also help monitor estates with infection clusters and keep track of the development trend of community outbreak. Now that we understand the significance of a strong sewage surveillance system, what can we do to further enhance it?
How to improve the sewage surveillance system?
Currently, the research team is working together with the Government on choosing a more suitable sewage sampling system. Below is a list of things the search team is working on to improve the sewage system:
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Developing new in-manhole sampling methods
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Simplifying the sample pre-treatment procedure
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Increasing the sampling and testing capacity
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Developing new methods for variants
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Integrating clinical/ epidemiological data
Along with the comprehensive data collected in the past months, it is likely for the sewage surveillance system to evolve into a more powerful tool to facilitate decision-making in fighting the SARS-CoV-2. Citizens can feel rest-assured knowing such system could play an active role in protecting us from both known pathogens and emerging pathogens alike as our city continue to speed toward futuristic advancement.
Header Image - Picture: Unsplash
