Professor Tong Zhang, Chair Professor (Environmental Engineering) of Department of Civil Engineering
The COVID-19 pandemic is over but researchers who spent days and nights, indeed months and years, helping the Government fight the virulent virus are not done with their battle.
Professor Tong Zhang, the Chair Professor (Environmental Engineering) of the Department of Civil Engineering at the University of Hong Kong (HKU), led a multidisciplinary sewage surveillance team of colleagues from environmental engineering and science, biological science, and public health, etc. during the COVID-19 pandemic to track and inform the public of the risk. The same technology is further developed today to control other pathogens, such as influenza virus, mpox virus, etc. It could be incorporated into an established sewage surveillance network to control for the emerging and re-emerging of pathogens in the community in Hong Kong, according to the Professor Zhang, an environmental engineering microbiologist.
But there is another prime task facing him and his team, that of tackling the worrying global threat of antimicrobial resistance (AMR). United Nations member states have been urged to address the pertinent issue, described by Professor Zhang as a grand global challenge of this century.
The Food and Agriculture Organization of the United Nations, the United Nations Environment Programme (UNEP), the World Health Organization (WHO) and the World Organisation for Animal Health (WOAH) have made joint calls for stepped-up global efforts to mitigate the risks of resistant infections.
It is estimated that AMR could take away 10 million lives annually by 2050 if no action is taken to stem its rise. “As noted by a prominent Oxford scholar, if COVID is an earthquake, then AMR is a tsunami,” Professor Zhang said.
In late May 2024, he delivered a talk at the 7th Environmental Dimension of Antimicrobial Resistance conference (EDAR7) in Montreal, Canada; sharing his insights with leading researchers from around the world, from fields including environmental engineering, environment science, chemistry, animal science, and public health.
Toward a universal unit for quantification of antibiotic resistance genes in environmental samples
A close link between environment and wastewater
Studying the genome of a vast amount of virus and bacteria seems a painstaking task, but Professor Zhang has obvious passion for the field with serious implications for public health in a highly urbanised world. During his doctoral studies at HKU in the late 1990s, after graduating from Nanjing University, he focused on the analytical tool via DNA to study micro-organisms, mainly bacteria in the environment.
He emphasises the value of wastewater. “It is not only flow of waste, but also of water for us to reuse, flow of resources to recycle, and flow of energy to recover. Furthermore, it is flow of information for us to understand the health of people in a city, the so-called wastewater-based epidemiology.”
In 2020, he was awarded a HK$34 million funding support for five years under the Research Grants Council’s Theme-Based Research Scheme for his project “Assess antibiotic resistome flows from pollution hotspots to environments and explore the control strategies”.
When COVID-19 struck Hong Kong in the same year, Professor Zhang and one postdoc and two PhD students, all of whom were young women scientists, reacted swiftly to the social request to identify any risk of an outbreak.
“Given our experience with sewage sampling, pre-treatment, and molecular detection/diagnosis, our work on COVID-19 virus wastewater surveillance is a natural extension of our previous research on wastewater surveillance of pathogens and antibiotic resistance genes” Professor Zhang recalled.
Professor Zhang and his research team worked on the wastewater surveillance during the pandemic
Surveillance work from 2020
Together with the Drainage Services Department (DSD) and the Environmental Protection Department, Professor Zhang and his team embarked on the unprecedented mission in April 2020, first by deciding on the proper sampling size for sites across the territory - which turned out to be a population of 30,000 in each site - and the basic principles and criteria for conducting wastewater surveillance at each location.
Professor Zhang also work closely with his collaborator in HKU’s Medical School, including Professor Gabriel Leung, Professor Malik Peiris and Professor Leo Poon. To ensure the validity of their measurement tool, they collected a de-activated virus from the lab of Professor Poon - a long-time collaborator with Professor Zhang’s team. “We put the de-activated virus into our sewage sample in our laboratory to validate our methodology,” he said.
By extracting the nucleic acid from infections in the sewage samples, Professor Zhang’s team checked for the presence of any strain of the virus. Any discovery made warranted an early warning signal to be sent to the Government, who would then relay the message to the public, and required residents in the infected areas to undergo compulsory testing.
Initially, DSD contractors installed sampling tools at 26 sites across Hong Kong for regular collection. Later to save time and cost, and avoid disrupting traffic when the tools were put inside and removed by opening manholes on the streets, the team invented autosamplers which could be installed inside the manholes, facilitating the large-scale application of sewage surveillance at the community level.
Sewage tests conducted by his team uncovered 60 cases of COVID between late 2020 and March 2021. A few months later, they made another timely discovery - the arrival of the Delta variant, the dominant variant overseas with a high death rate.
A prototype of the sampling tool for taking sewage samples
The first to uncover a delta case
Professor Zhang remembers the day and sequence of events in June 2021, when after midnight, he received a call from his team member informing him of the test result that showed the presence of the particular variant.
“I was awaiting the result,” he said. “The next morning the four of us discussed it in the office. After lunchtime, I told the Government that we had discovered the variant with high probability. Later, the Government announced its decision to ask the 15,000 people in an area of Tai Po to take compulsory tests.”
The first Delta case was confirmed three days later, after the patient involved had undertook a test. “We gave the Government the first information about the Delta case here,” he recalled. “Our variant tests also provided important real-time information about the spread of the highly infectious Omicron and other variants during the 5th wave of the pandemic starting from January of 2022,” he recalled.
Continuous, routine inspection
For a year till the end of 2021, his team worked day and night, often finishing writing reports on data analysis for the Hong Kong Government just before midnight.
After wastewater surveillance at the community level became routine, the surveillance work was gradually taken over by government contractors. Having obtained a patent for their testing methods, Professor Zhang’s team also designed a quality control and assurance programme to ensure the reliability of data, and provided training for the contractors.
In 2021, Professor Zhang was given the HKU Innovator Award, as well as the Medal of Honour by the HKSAR Government in recognition of his contributions in fighting against COVID-19. His research team was awarded the Chief Executive’s Commendation for Community Service for their outstanding contribution to the historic work, which caught much media attention. In addition, their surveillance method and autosampler won the Gold Medals of The International Exhibition of Geneva Inventions.
“Collaboration among team members is very important,” noted Professor Zhang “There are many hardworking people that should be acknowledged, including PhD students, postdocs, and staff from different units of the government. Without their great efforts, we could not have completed the project.”
Now with 20 members, his team has developed databases, tools and demonstrated some important research directions, and standards for wastewater surveillance. Their works were published in leading journals such as the Environmental Health Perspective, Water Research, Environmental Science and Technology, etc.
Now that the COVID virus, though still highly prevalent in Hong Kong, has become very weak. For continuous tracking of the trend, it is far more effective to test samples at wastewater treatment plants alone, he thinks. “The samples there are more representative and can be taken at much lower cost.”
The previous pandemic-focused work undoubtedly marks a memorable period in his career. It is, nonetheless, just part of a whole spectrum of research areas that fascinate a dedicated microbiologist like him.
Professor Zhang (left) received the HKU Excellence Awards 2020 - Outstanding Researcher Award
An array of research topics
Having lived in Hong Kong for the past 26 years, Professor Zhang cites a range of areas in wastewater-based epidemiology worth investigating in the years ahead. They include interpreting sewage data using epidemiological models, developing standards for testing for comparison of data in different areas, developing more cost-effective and representative sampling approaches and pre-treatment methods, automation of the technical flow from sampling to data interpretation and decision-making platforms, etc.
Above all, he is concerned about projects with global impact, such as developing cost-effective measures for detecting viruses especially for low and middle-income countries.
“Hong Kong can afford the testing cost, but for low and middle-income countries, they can’t. So, we are doing research to see if we can develop cheaper methods to achieve the same effectiveness,” said Professor Zhang.
Further enhancing the sampling process also aligns with the global trend of developing smart cities. “We are working on producing automatic, on-site all-in-one devices to collect samples, do the detection and have the result sent to cloud,” said Professor Zhang. “Then nobody will need to go to take samples, and testing can be done on a more routine basis, saving manpower.”
His team is set to continue to work on what he calls the “Environment-Microbiome-Health axis”, by using innovative molecular techniques, AI, big data analysis, and collaborating with colleagues from different disciplines. “The study on microbiome will help to build a healthy city if we have smart designs,” he said.
Research on studying environmental microbiome and tackling AMR will remain significant. “It will have long-lasting global impact. It is more challenging than COVID.”