Sewage testing is a very cost effective and powerful tool for early detection and containment of COVID-19 transmission in the community, according to Peter Grevatt, CEO of the Water Research Foundation.

Unlike individual tests, wastewater testing can provide "a picture of an entire community," and help track trends, said Grevatt, adding "the wastewater in a community actually has a story to tell about the public health status of that community."

Traces of the SARS-CoV-2, that virus that causes COVID-19, have been found in many countries' sewage, including Brazil, Spain and Italy.

Sewage sampling, which is usually done to test the efficacy of wastewater treatment plants, has become a key tool in tracing the novel coronavirus.

Applied in a number of locations worldwide, the tool is able to identify the presence of COVID-19 in community as much as a week before clinical testing, according to Grevatt, saying it is particularly powerful when used in a community that is on an exponential growth curve of increasing cases of COVID-19.

In a community in the Netherlands, "the first signal from sewer shed monitoring came in about six days before the first individual within that community was identified as positive for COVID-19."

Wastewater testing also contributes to detecting the source of a COVID-19 outbreak, in a way that requires much less labor.

Grevatt said with wastewater sampling, it is able to identify as few as one to three cases in 100,000 population.

"And if you imagine how many clinical tests you would have to perform to find one to three cases per 100,000, and you realize that you could do this with just a handful of test of a central wastewater treatment plant, you start to see the power of this tool. "

Wastewater testing has been used for decades to track diseases, such as the presence of poliovirus.

Countries carry out nationwide sewage testing

In The Netherlands, the National Institute for Public Health and the Environment (RIVM) has been analyzing sewage water for the presence of COVID-19 at several sites across the country since February, and will test all the water treatment plants in the country.

Italy's main health body Istituto Superiore di Sanità (ISS) also started a pilot study of 15 sites in tourist areas in July, and aims to set up a national testing system in October involving 100 cities covering over 60,000 residents.

"In that way we could have a satellite of the country… for the early warning of the circulation of the virus in cities maybe before clinical cases," said Luca Lucentini from ISS.