SARS-CoV-2 in wastewater

The presence of SARS-CoV-2 in human feces is confirmed by the detection of specific viral ribonucleic acid (RNA) sequences that are unique to SARS-CoV-2. SARS-CoV-2 RNA has been detected in feces of not only symptomatic but also asymptomatic patients.

Wastewater sampling captures the aggregated community viral signal, and can potentially be used to identify regions where disease incidence is increasing, but remains undetected via individual clinical testing.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is responsible for causing the respiratory disease termed Corona Virus Disease-19 (COVID-19).

On 5 March 2020, the first locally confirmed COVID-19 case in South Africa was announced.

Symptoms reported for patients with COVID-19 have included mild to severe respiratory illness such as coughing, sore throat, shortness of breath, fever or gastrointestinal symptoms such as diarrhoea.

Wastewater-based epidemiology (WBE) is an approach to predict the potential spread of an infection by testing for infectious agents in wastewater, and obtain information on health, disease, and pathogens.

South Africa currently has the capacity to conduct 5 000 tests for COVID-19 daily. Thus, an additional method for near real time tracking of disease spread at a population level is needed.

The screening of wastewater, as a public health surveillance tool, can be used to observe community-level trends through analysis of wastewater to make inferences about the population.

Frequently Asked Questions (FAQs)

Thus far, there is no scientific evidence confirming the transmission of the virus through faeces or wastewater. Non-live SARS-CoV-2 RNA is being detected in the wastewater, and there is no credible evidence to suggest that it is contagious.

The monitoring of SARS-CoV-2 in wastewater is conducted at selected wastewater treatment plants in the Western Cape, Eastern Cape, Limpopo and Gauteng provinces of South Africa.

On Mondays, grab wastewater samples are collected from wastewater treatment plants included in the project by trained wastewater samplers. Samples are collected at approximately the same time every week. As soon as possible after collection, wastewater samples are transported under refrigerated conditions to the analytical laboratory. Please refer to the Wastewater Sampling Guide that has been developed for the purposes of the SAMRC wastewater surveillance for SARS-CoV-2. (SARS-CoV-2 Wastewater Sampling Guide)

The samples are analysed at SAMRC or partner university-based laboratories. The laboratory confirms the presence (qualitative analysis) and determines the RNA copy number of SARS-CoV-2 viral RNA by reverse transcription polymerase chain reaction (RT-PCR) (quantitative) analysis. Results for each wastewater treatment plant are then aggregated and presented as the RNA copies per millilitre (RNA copies/ml) found in the wastewater samples.

There is the potential for broader application of wastewater-based surveillance in South Africa to similarly develop a public health early warning system for diseases such hepatitis A, measles and norovirus.

This programme has brought together professionals and experts spanning skill sets, disciplines and sectors including public health, microbiology, town planning and wastewater treatment facilities.