A study carried out by the Italian National Institute of Health (ISS) found traces of SARS-CoV-2, responsible for the coronavirus disease COVID-19, in Milan and Turin’s wastewater in December, several months before the country confirmed the first cases of the infection, reports the BBC.
This evidence adds to the indication from other countries that the coronavirus could have been circulating months before cases were officially confirmed.
In China, authorities confirmed the first cases in December, and Italy was one of the first European countries to report cases in mid-February.
The study examined 40 wastewater samples collected between October 2019 and February 2020, and 24 control samples collected between September 2018 - June 2019 that made it possible to exclude with certainty the presence of the virus.
The results were confirmed by two different laboratories that used two different methods. The presence of SARS-CoV-2 was first found in the wastewater samples of Turin and Milan on 18 December and in Bologna on 29 December. Traces of the virus were also found in the following months of January and February in Milan, Turin and Bologna. Meanwhile, the samples taken in October and November of 2019 showed negative results.
In the city of Barcelona, in Spain, a study found traces of the virus in wastewater samples collected mid-January, approximately 40 days before the city reported its first case.
The ISS water quality expert, Giuseppina La Rosa, said that these findings could help scientists understand how the virus began spreading in the country.
Luca Lucentini, director of the ISS Water Quality Department, said: "Our results confirm the consolidated international evidence on the strategic role of virus surveillance in samples taken regularly in wastewater and at wastewater treatment plants, as a tool to detect and monitor the circulation of the virus in different territories at an early stage."
However, Lucentini believes that the discovery of the virus does not automatically imply that the chains of transmission that led to the development of the epidemic in Italy originated from these first cases.
The town of Codogno, in the province of Lodi, Lombardy, was where the first non-imported virus case in Italy was confirmed. On 21 February, the town went into lockdown and was declared a “red zone”. The rest of the country was closed off at the beginning of March.
Researchers at the ISS believe that studying Italy’s wastewater can be an effective way of controlling the epidemic, as it can signal the virus’s presence before cases are confirmed.
In July, the Italian National Institute of Health will be launching a pilot study monitoring wastewater at tourist resorts. Then, based on these results, the Institute hopes to carry out a nationwide wastewater surveillance project in the fall.