The Italian National Institute of Health (ISS) examined 40 sewage samples collected from wastewater treatment plants in northern Italy between October 2019 and February 2020.

An analysis released last Thursday said samples taken in Milan and Turin on December 18 showed the presence of the SARS-Cov-2 virus.

“This research may help us understand the beginning of virus circulation in Italy,” Giuseppina La Rosa, an expert in environmental wastewater at the ISS who co-led the research, said.

Studies conducted by scientific teams in the Netherlands, France, Australia and elsewhere have found signs that the virus that causes COVID-19 can be detected in sewage, and many countries are beginning to use wastewater sampling to track the spread of the disease.

Scientists said the detection of traces of the virus before the end of 2019 was consistent with evidence emerging in other countries that COVID-19 may have been circulating before China reported the first cases of a new disease on December 31.

A study in May by French scientists found that a man was infected with COVID-19 as early as December 27, nearly a month before France confirmed its first cases.

La Rosa said the presence of the virus in the Italian waste samples did not “automatically imply that the main transmission chains that led to the development of the epidemic in our country originated from these very first cases”.

Samples positive for traces of the virus that causes COVID-19 were also found in sewage from Bologna, Milan and Turin in January and February 2020.

Samples from October and November 2019 were negative, showing the virus had yet to arrive, La Rosa said.

The ISS said it had urged the health ministry to coordinate the collection of samples regularly in sewers and at the entrance to purification plants “as a tool to detect and monitor the circulation of the virus in different territories at an early stage”.

 It plans to launch a pilot study on priority sites identified in tourist resorts in July, and is expected to setup a nationwide surveillance network of waste water by autumn.

Italy was the first European country to be hit by coronavirus and the first in the world to impose a nationwide lockdown.

The nation has now recorded more than 34,600 deaths from the virus.

With AAP