Coronavirus was present in Barcelona waste waters on March 12, 2019: Study
Covid-19 was announced in Wuhan, China in early December in 2019 and reached every place worldwide later, including Europe.
The first case in Europe was announced in France in late January 2020 but this chronology on the evolution of the disease can change according to a study led by the University of Barcelona, in collaboration with Aigues de Barcelona.
"All samples were negatives regarding the SARS-CoV-2 genome presence except for March 12, 2019, in which the levels of SARS-CoV-2 were low but were positive, using two different targets", the researchers wrote.
The results which have been published in the research archive medRxiv and are yet to be peer-reviewed, suggest the infection was present before knowing about any case of Covid-19 in any part of the world.
Barcelona receives many visitors for both tourist and professional reasons and it is possible for a similar situation to have taken place in other parts of the world.
"Since most of the Covid-19 cases show a similar symptomatology to the flu, those cases could have been disguised as an undiagnosed flu," the authors said.
As part of the sentinel surveillance project, the researchers analysed weekly obtained samples in two big water treatment plants in Barcelona.
"The levels of the SARS-CoV-2 genome coincided with the evolution of Covid-19 cases in the population", said Albert Bosch, professor and coordinator of the study.
Later, researchers analysed frozen samples from previous months to the systematic sampling, which revealed the growing apparition of SARS-CoV-2 genome between early January and early March in 2020, bringing the chronology of the new coronavirus arrival in Spain even earlier.
The presence of the Covid-19 virus was detected in Spain on January 15, 41 days before the announcement of the first reported case of Covid-19 in the country on February 25.
According to the researchers, the new results show the validity of the surveillance of waste waters to anticipate cases, especially considering the significant contribution of the asymptomatic and pre-symptomatic carriers in the spreading of the virus.
"Those infected with COVID-19 could have been diagnosed with flu in primary care by mistake, contributing to the community transmission before the public health took measures", said Bosch, also the president of the Spanish Society of Virology.
"In the specific case of Barcelona, having detected the SARS-CoV-2 spread a month before could have improved the response to the pandemic," he noted.
Although Covid-19 is a respiratory disease, researchers proved there are large quantities of the coronavirus genome in the excrements that reach waste waters.
This situation made the waste water-based epidemiology a potential tool for an early detection of the circulation of the virus among the population, especially considering the important presence of asymptomatic people who transmit the virus, said the study.
Independent experts, however, have questioned the Spanish study which is yet to be peer-reviewed, saying "other lines of evidence strongly suggest the virus emerged in China last year," reports The New York Times.