The COVID-19 pandemic has reignited interest in wastewater surveillance, which involves monitoring sewage systems for the presence of viruses, bacteria, and other pathogens. Non-infectious fragments of the virus’s genetic material have been discovered in untreated wastewater worldwide.
COVID-19 wastewater surveillance could have numerous advantages. It is a low-cost method of surveying the transmission dynamics of entire communities. It is free of the biases that other epidemiological indicators have. It collects information from people who do not have access to healthcare. If it is successful in revealing infection dynamics before diagnostic testing, it could provide public-health officials with near-real-time disease prevalence data.
The National Environment Agency (NEA) has also taken the initiative to implement the programme and will be expanding its wastewater surveillance programme to cover more than 400 sites by next year, the agency recently announced. Since February of last year, more than 200 sites, including workers’ dormitories, student hostels, welfare and nursing homes, and residential sites, have been under surveillance.
Wastewater testing is a “non-intrusive” way to detect COVID-19 transmission in a community and supports the monitoring and management of the coronavirus, NEA said. “With the clearance of transmission in dormitories, wastewater surveillance today complements rostered routine testing of individuals for early detection of COVID-19 transmission in dormitories, to facilitate early intervention and isolation of cases.”
COVID-related legislation was recently enacted. The discovery of 19 viral fragments in wastewater from several neighbourhoods, including Bukit Merah View, Hougang, and Yishun, prompted authorities to conduct swab tests on residents and visitors. According to the NEA, more than 15 cases were discovered in June of this year.
At a media briefing in Beo Crescent, the director of microbiology and molecular epidemiology division at NEA’s Environment Health Institute demonstrated the use of an autosampler – a device pre-programmed to draw wastewater samples for testing.
The device enables NEA to customise the sampling programme and make changes based on whether it intends to collect samples throughout the day or during peak sewage activity. As a matter of fact, wastewater testing can serve as a warning system for the presence of COVID-19 cases, and the trending of SARS-CoV-2 concentration over time can determine whether infection control measures have been effective.
One limitation of wastewater surveillance is that it cannot identify the individuals who have been infected. “Social media syndromic analysis,” in which social media posts are searched for descriptions of symptoms consistent with a given disease, has emerged as an effective tool for surveillance of infectious diseases including COVID-19.
Combining wastewater monitoring and social media analysis could detect community outbreaks that would otherwise go undetected because the method identifies infected people who aren’t yet showing symptoms (presymptomatic) or who don’t show symptoms at all (asymptomatic). This information can be used by public health officials to reinforce physical distancing and other isolation practices such as targeted testing of individuals to restrict community spread of the disease.
Monitoring is ongoing to determine the trending of viral material concentrations at water reclamation plants, as well as the relationship between viral material concentration and COVID-19 prevalence in Singapore.
The methodology for wastewater sampling and testing for COVID-19 was developed by NEA’s Environmental Health Institute, with scientific inputs from the Singapore Centre for Environmental Life Sciences at the Nanyang Technological University, Singapore-Massachusetts Institute of Technology Alliance for Research and Technology and the National University of Singapore.
In contrast, increased international travel and globalisation, on the other hand, have resulted in the rapid spread of infectious diseases. To combat this, global infectious disease surveillance must be conducted in real-time or near real-time and must go beyond simply counting the number of infected people to include the ability to recognise novel disease patterns. The low cost, speed, and capability of wastewater surveillance to detect emerging pathogens before they become endemic improve the ability to respond to disease outbreaks quickly, reducing global illness and death.