The discovery of virus genome presence so early in Spain, if confirmed, would imply the disease may have appeared much earlier than the scientific community thought.
"We found traces of the virus in a single sample from March 2019 and then never again until 2020", said Albert Bosch, the university's research leader.
Since April 13 this year, the researchers have analyzed weekly the samples obtained from Barcelona's two major water treatment plants, and after seeing a strong correlation between the presence of coronavirus in waste water and the number of cases in the population, they chose to go further.
Both symptomatic and asymptomatic carriers of COVID-19 shed the virus in their feces, making sewage surveillance a powerful tool for monitoring the spread of the disease throughout the community. They first found traces of the virus in a sample from January 15, 2020, after which they ran the tests of the samples taken between January 2018 and December 2019. While the study published in the medRxiv repository is not peer-reviewed up to now, the revelation was extensively covered by the Spanish media, such as the El Mundo daily.
Italian scientists have also said they found COVID-19 genetic material present in sewage months before the virus turned northern Italy into the global COVID-19 hotspot.
"When it's just one result, you always want more data, more studies, more samples to confirm it and rule out a laboratory error or a methodological problem", he said. There are chances that of a false positive due to the similarities of the virus with other respiratory infections. "It's definitely interesting, it's suggestive".
Professor Bosch said early patients were probably wrongly diagnosed with common flu, and that earlier detection of COVID-19 would have improved the response to the pandemic.
Spain has been one of the countries hardest-hit by the virus, with more than 28,000 deaths, and had one of the world's strictest lockdowns as residents were kept inside apart from trips for food, medicines and essential jobs.
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