Sewage Study Suggests Coronavirus Was Already Circulating in Northern Italy in December 2019

Scientists in Italy have found traces of the new coronavirus in wastewater collected from Milan and Turin in December 2019 - suggesting COVID-19 was already circulating in northern Italy before China reported the first cases.

The Italian National Institute of Health looked at 40 sewage samples collected from wastewater treatment plants in northern Italy between October 2019 and February 2020. An analysis released late on Thursday said samples taken in Milan and Turin on Dec. 18 showed the presence of the SARS-Cov-2 virus.

"This research may help us understand the beginning of virus circulation in Italy," said Giuseppina La Rosa, an expert in environmental wastewater at the Italian National Institute of Health who co-led the research.

Small 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 Dec. 31.

"That COVID-19 could have been circulating in Italy is possible," said Rowland Kao, a veterinary epidemiology and data science professor at Scotland's Edinburgh University.

"(This finding) does not on its own, however, tell us if that early detection was the source of the very large epidemic in Italy, or if that was due to a later introduction into the country."

A study in May by French scientists found that a man was infected with COVID-19 as early as Dec. 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 taken in October and November 2019 tested negative.

The institute said it plans to launch a pilot study in July to monitor wastewater at sites identified in tourist resorts.