The study that stated that the new coronavirus could already circulate in wastewater in Spain in March last year is raising doubts among experts. At El País, there were several questioned the methodology that the research team used.
THE concerned study, carried out by the University of Barcelona, was released this Friday. The team of virologists analyzed water samples from two treatment plants in the city collected between January 2018 and May 2020. Of all those collected before the pandemic, only in one, collected in March 2019, SARS-CoV-2 was detected – which suggested that the Covid-19 virus had been in Spain for over a year.
This surprising discovery indicates that the virus was circulating in Barcelona long before any case of Covid-19 in the world was confirmed, ”the investigators said in a statement.
But several experts are skeptical about this study – which is still in the pre-publication phase. Pilar Domingo, virologist at the University of Valencia, argues that “there is a lack of scientific data to correctly evaluate the result”. “I don’t say that [os investigadores] incorrect, but the values they show are very close to the limit, very close to the negative threshold. In another type of study, [o resultado] it would be negative ”, he explained.
Damià Barceló, a researcher at ICRA, a Catalan institute that develops studies related to water, warned that it is still not known whether the virus can be found in such old samples and questions the methodology that the team followed.
There is no standardized methodology and an analysis of wastewater can give many errors. It’s not like testing blood. There are many sampling protocols for Covid-19 in wastewater and each one gives different results ”, he explains.
Fernando González, professor of genetics at the University of Valencia, recalled that “other cities with more international visitors than Barcelona did not detect the virus in their analyzes of wastewater”.
In the same vein, Luca Cozzuto, data analysis coordinator at the Genomic Regulation Center in Barcelona, questions why the virus was not found in samples collected after March 2019. Recalling that “an infected person would not be enough to detect the virus in the wastewater ”, the expert explains that“ a greater number of foreigners on vacation in Barcelona ”would be needed to“ leave virus particles in the water, without infecting anyone else ”. “Or there was a hidden outbreak before September“, He points out.
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