Italian researchers say traces of the coronavirus responsible for the Covid-19 pandemic were found in sewage water samples taken as early as last December, giving a clearer picture of how the infection spread to Europe.
The study was reported by Istituto Superiore di Sanita (ISS), the research branch of Italy’s national health service. Its scientists collected samples from sewage systems before matter entered treatment facilities and tested them for the presence of RNA specific to SARS-CoV-2. The test was positive as early as December 18, 2019 in Milan and Turin and as early as January 29 in Bologna, ISS reported.
The research was part of regular surveillance of sewage water that Italian scientists, led by molecular biologist Giuseppina La Rosa, have been conducting since 2007. The samples that tested positive were compared against those collected between September 2018 and June 2019, in which no traces of the virus were found.
The results should not be presumed to imply that Milan and Turin are the cities where the Covid-19 outbreak in Italy originated, the scientists warn. Rather, they are a proof that testing sewage water for viral RNA can be an effective tool for detection and control of infections. The researchers plan to start a pilot project in July, which will monitor popular tourist destinations for early signs of Covid-19 in their sewers.
“Based on the results of the pilot study, we hope to be ready to conduct surveillance across the nation in the potentially most critical period of autumn,” said Lucia Bonadonna, director of the Department of Environment and Health of ISS.
The World Health Organization (WHO) didn’t declare the novel coronavirus a matter of international concern until late January. But later studies suggest that the infection had made its way out of China much earlier, and was already affecting patients in countries like France in December 2019.
The timeline of Covid-19’s spread has also become a political issue, after the US accused China and WHO of covering up the severity of the disease and, thus, of not giving other nations time to prepare for the pandemic. Beijing says these accusations are false and are meant to shift the blame for the high death toll that the coronavirus has claimed in the US.