Italian researchers say sewage from two cities contained traces of coronavirus in December, long before the country’s premiere of confirmed cases.
The National Institute of Health (ISS), said to water from Milan and Turin, showed trace virus genetics on December 18.
He adds evidence from other countries that the virus may have been circulating much earlier than previously thought.
Chinese officials confirmed the first case in late December. In Italy, the first case was in mid-February.
In French May, scientists said tests on samples showed a patient treated for suspected pneumonia near Paris on December 27 actually got the coronavirus.
Meanwhile, in Spain, a study found the trace virus in the wastewater collected in mid-January in Barcelona, about 40 days before the first case was discovered.
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In their study, ISS, the scientists examined 40 samples of wastewater collected from wastewater treatment plants in northern Italy between October and February.
Samples from October and November came back negative, showing that the virus had not yet arrived, ISS water quality expert Giuseppina La Rosa said. Sewage from Bologna showed traces of the virus in the month of January.
The results could help scientists understand how the virus began to spread in Italy, La Rosa said.
However, she said that the research did not “automatically imply that the main chains of transmission that allowed the development of the epidemic in our country of origin of these first cases”.
Italy is first known not imported the case virus is a patient in the city of Codogno in the region of Lombardy. The city was closed and declared a “red zone” on February 21. Nine other cities in Lombardy and its neighboring Veneto followed and the whole country went into lockdown in early March.
The ISS said the results confirmed the “strategic importance” of sewage to water as an early detection tool, as it can signal the virus from the presence of clinically confirmed cases before. Many countries are now using the technique.
The institute says it aims to start a pilot project to track water waste at tourist resorts in July with a view of the National Waste Establishment, a water monitoring network later this year.
More than 40,000 people died from Covid-19 in Italy.