Experts say wastewater COVID testing is still useful, even as the virus becomes more widespread. 

Wastewater surveillance was used as an important early warning system in the COVID-19 pandemic, but now, many state and territory governments are reducing testing programs. 

CSIRO Land and Water Director Dr Paul Bertsch says that despite the decline in wastewater surveillance, sewage testing is still important in helping to predict infection rates and hospitalisation peaks. 

“When we shifted from a 'managing to zero policy' to now opening the borders and accepting Omicron is going to be pervasive in the community, the interest in wastewater by many municipalities has decreased,” he said.

Past sewage surveillance efforts testing for SARS-CoV-2 detected the presence or absence of the virus, but it is now expected that the virus will be present in most places. 

Still, it is useful to test for the amount of virus present in samples, using the extent of prevalence to predict peaks in infections and hospitalisations.

“The peak in wastewater typically precedes the peak in clinically determined infections by anywhere between five to 21 days, and on average, globally, it's 10 days,” Dr Bertsch says. 

There is also potential for data monitoring to continue to offer insights into viral concentration and trends, as well as continue to provide warning to vulnerable communities.

“How wastewater-based epidemiology can be used more broadly, even when you have a significant prevalence of infectivity in the community, the appreciation for that just doesn't seem to have been developed yet,” Dr Bertsch said.

The various decisions to reduce the level of sewage surveillance has largely been a matter of resources, as wide-scale monitoring is resource intensive.

However,  Daniel Deere - the water, sanitation and hygiene consultant leading the development of the World Health Organization's guidelines for environmental monitoring of COVID - has called for Australian Government funding to cover the costs of the surveillance programs.

“The time has come now for more federal leadership in this area,” he says.

“If we look at what has happened in the US and European Union, we're seeing that rather than having state-by-state or country-by-country programs, there's a move to have more alignment in methods, sharing of data and information and funding support, and that will lead to better outcomes.”