Virus was in Italy in December
Study shows pathogen in cities’ sewers two months before outbreak
The novel coronavirus was already present in two large cities in Italy in December, over two months before the first case was detected, a national health institute study of waste water found.
Researchers discovered genetic traces of Sars-Cov-2 – as the virus is officially known – in samples of waste water collected in Milan and Turin at the end of last year, and Bologna in January, the ISS institute (Italian National Institute of Health) said in a statement yesterday.
Italy’s first known native case was discovered mid-February.
The results “help to understand the start of the circulation of the virus in Italy”, the ISS said.
They also “confirm... consolidated international evidence” as to the strategic function of sewer samples for early detection, it added.
Italy was the first European country to be hit by the virus and the first in the world to impose a nationwide lockdown.
The first known case, other than a couple of visiting Chinese tourists, was a patient in the town of Codogno in the Lombardy region.
On Feb 21, the government designated Codogno as a so-called red zone and ordered it shuttered, followed by nine other towns across Lombardy and Veneto.
By early March it extended the shutdown across the country. Italy has recorded over 34,500 deaths.
ISS’ water quality expert Giuseppina La Rosa and her team examined 40 waste water samples from October 2019 to February 2020.
The results, confirmed in two different labs by two different methods, showed the virus’ presence in samples taken in Milan and Turin on December 18, 2019 and in Bologna on January 29, 2020.
Samples from October and November 2019 were negative, showing the virus had yet to arrive, La Rosa said.
Waste water testing could signal the presence of the virus even before the first cases are clinically confirmed in areas untouched by the epidemic or where it has ebbed.
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”.