Sewage can help track Covid-19

Study finds Sars-CoV-2 nucleic acids in wastewater

THE answer to how Sars-CoV-2 is spreading in the country might be found in a surprising source: sewage.

Recent research has shown the presence of Sars-Cov-2 nucleic acids in the faeces of infected people and wastewater from infected communities, according to the Water Research Commission, though no infective strain had been confirmed.

There was increased interest, the commission said, in the presence and persistence of the virus in the “water and sanitation environment, the role of the aquatic environment in the transport and possible transmission through exposure to contaminated surface water sources, poorly treated municipal wastewater and the faeces of infected people”.

Last week, the commission unveiled a national wastewater-based epidemiological study for the surveillance of Covid-19 spread in communities.

“This could provide a rapid and effective way to predict the potential spread of Covid19

by picking up on biomarkers in faeces and urine from disease carriers that enter the sewer system.”

Rapid testing kits using paper-based devices could be used at wastewater treatment plants to trace sources and determine whether there were potential Covid-19 carriers in areas.

“This could lead to an early warning system for Covid-19 in any second- or third-wave predictions and provide preparedness for future pandemics.”

The commission’s Nonhlanhla Kalebaila and Stanley Liphadzi said developing countries might not be able to afford or implement mass-screening programmes to uncover new infections – a “huge challenge as the pandemic peaks”.

“However, there is an opportunity of tracing of Covid-19 spread in sewered wastewater treatment systems and non-sewered sanitation systems. This promises to provide us with information that could track and signal hot spots of community transmission.”

The virus is shed primarily from the respiratory and gastrointestinal tract. “Studies suggest the virus may survive in stool samples for three to four days. Interconnectedness of the wastewater plumbing network can facilitate exposure, as in Hong Kong.”

Professor Anthony Turton of the University of the Free Sate’s centre for environmental management said the major risk arising from Covid-19 was the fact that people could be infected but show no symptoms. He said since the government cannot test every citizen, sewage surveillance was key.

“We have 824 wastewater treatment works in South Africa. Each of these serves a population of known size.

“By taking samples of sewage according to a defined protocol, it is now technically possible to determine the viral load of the entire population in the catchment area of that sewage works. This data can be compared weekly, and we can determine if the total viral load is increasing or decreasing.

“This is easier than testing millions of citizens, the results of which only give a snapshot of information relevant at that precise moment in time.”