The media reported recently that the Health Ministry had detected SARS-CoV-2 in wastewater at airports.
It was also reported that China had begun SARS-CoV-2 wastewater surveillance in selected cities after the cessation of its 'Zero Covid' policy.
Wastewater is primarily defined as water that is flushed down toilets and enters the sewage treatment system. It represents the pooled faecal sample of the communities linked to the sewage system.
Wastewater surveillance is done for pathogens that are excreted in human faeces.
It provides a rapid real-time snapshot of the prevalence of disease in the community.
It also addresses challenges of disease underreporting due to asymptomatic infections, self-home treatment, and delayed or absent notifications from medical practitioners.
Information from wastewater surveillance can be used to monitor disease burden patterns, reintroduction or emergence of a new pathogen/variant, and even evaluate the impact of community behavioural campaigns such as masking and physical distancing.
An example of the importance of wastewater surveillance is the detection, in 2022, of wild poliovirus in sewage samples in London and New York before any clinical cases were reported.
This prompted the local health authorities to implement immediate measures to enhance the coverage of primary polio vaccination together with polio boosters in at-risk communities.
Information from an effective wastewater surveillance system can greatly complement notification systems. It enables health authorities to implement prompt and targeted interventions before an outbreak occurs in a community.
Hong Kong detected the Delta variant in sewage samples at the end of December 2020. The people were then informed about the common symptoms, and the importance of continuing physical distancing and masking, in addition to hand hygiene and respiratory etiquette.
In July 2022, researchers reported that sampling of community wastewater in San Diego, California, detected the presence of the Alpha, Delta, Epsilon and Omicron variants up to 14 days before they started showing up on nasal swabs.
This implies that wastewater surveillance applied to transportation-based sanitation systems can serve as an early indicator of possible community transmission.
The people need not be alarmed by the news of the detection of the SARS-CoV-2 virus in human waste. The Health Ministry's initial reports show that the variants are already in circulation in Malaysia and the risk posed to human health and the environment is minimal.
All in all, wastewater surveillance in Covid-19 control is important for several reasons.
Firstly, by measuring SARS-CoV-2 levels in untreated sewage over time, public health officials can determine if infections are increasing or decreasing in a community.
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