Genetic material of the novel coronavirus was detected in the samples collected from Milan and Turin sewage last December, according to an announcement released by an Italian institution on Thursday.

The study, conducted by the Istituto Superiore di Sanità, one of the leading institutions of the Italian National Health Service, suggests the virus already existed in wastewater collected from the entrance of treatment plants in northern Italy before the country's first COVID-19 case being reported.

40 samples from October 2019 to February 2020 and 24 samples from September 2018 through June 2019 serving as a control group to rule out the possibility of the presence of the virus have been analyzed, according to researchers.

"Results confirmed by two different methods in two different laboratories indicate the presence of SARS-COV-2 RNA in samples taken in Milan and Turin on December 18, 2019 and in Bologna on January, 29, 2020," said Giuseppina La Rosa at the Department of Environment and Health of the Italian National Health Institute.

In an earlier study published in April, scientists also found SARS-CoV-2 in wastewater collected in areas of high (Milan) and low (Rome) epidemic circulation. One of the positive results was obtained in a Milan wastewater sample collected a few days after the first notified Italian case.

Authors noted the science of sewage surveillance could be deployed in countries across the world to help monitor the spread of national epidemics of COVID-19 while reducing the need for mass testing.

"Most people know that you emit lots of this virus through respiratory particles in droplets from the lungs, but what's less well known is that you actually emit more small virus particles in feces," Davey Jones, a professor of environmental science at Britain's Bangor University, told Reuters.

This suggests that on a wider scale, sewage sampling would be able to estimate the approximate number of people infected in a geographic area without having to test every person.