COVID-19 was announced in Wuhan (China) in early December in 2019 and it would reach every place worldwide later, including Europe. The first case in Europe was announced in France in late January 2020. This chronology on the evolution of the disease can change according to a study led by the University of Barcelona, in collaboration with Aigües de Barcelona.

Researchers detected the presence of the virus that caused the disease in samples of waste water in Barcelona, collected in March 12, 2019. These results, sent to a high impact journal and published in the archive medRxiv, suggest the infection was present before knowing about any case of COVID-19 in any part of the world.

This study, which counts on the participation of the researchers of theGroup on Enteric Virus of the UB Gemma Chavarria Miró, Eduard Anfruns Estrada and Susana Guix, led by Rosa Maria Pintó and Albert Bosch, is part of the project on sentinel surveillance of SARS-CoV-2. This initiative is coordinated by this research group, in collaboration with Aigües de Barcelona and funded by the REVEAL project, from the company SUEZ, in order to detect the virus in waste waters and adopt immediate measures considering future COVID-19 outbreaks.

An early detection tool

Altohugh 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 population, especially considering the important presence of asymptomatic people, especially considering the important presence of asymptomatic and asymptomatic people who transmit the virus.

As part of the sentinel surveillance project, and after April 13, the researchers analysed weekly the 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”, notes Albert Bosch, professor at the Faculty of Biology of the UB and coordinator of the study.

COVID-19 cases hidden by the flu

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 coronavirus arrival in Spain even earlier: the presence of the virus was detected in January 15, 41 days before the announcement of the first case of COVID-19, which was announced on February 25.

According to the researchers, these results show the validity of the surveillance of waste waters to anticipate cases, specially 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”, notes Albert Bosch, also president of the Spanish Society of Virology.

“In the specific case of Barcelona –the virologist continues–, having detected the SARS-CoV-2 spread a month before could have improved the response to the pandemic”.

Analysis of frozen samples from 2018 and 2019

These results encouraged the researchers to analyse some frozen samples between January 2018 and December 2019, with the shocking results of the presence of SARS-CoV-2 genome in March 2019, before any notification of COVID-19 cases in the world. “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”, says the researcher.

“Barcelona receives many visitors for both tourist and professional reasons, –continues Bosch–, and it is possible for a similar situation to have taken place in other parts of the world, and since most of the COVID-19 cases show a similar symptomatology to the flu, those cases could have been disguised as an undiagnosed flu”.

Models in the SARS-CoV-2 epidemiological surveillance

The Group on Enteric Viruses is also in charge of the scientific coordination of a project on the SARS-CoV-2 sentinel surveillance in waste waters in Spain, funded by the Spanish Ministry for Ecological Transition and Demographic Challenge. This task counts on the participation of two groups from CSIC, the Institute of Agrochemistry and Food Technology (IATA-CSIC) and the Centre of Edafology and Applied Biology of Segura (CEBAS), as well as a group from the University of Santiago de Compostela. Moreover, together with the research group Microbiology of Water related to the Health (MARS) of the UB, led by Anicet Blanch, coordinates the surveillance of the same virus in Spanish waters.

Last, this group also takes part in a monitoring project on the presence of SARS-CoV-2 in waste waters in the entrance of Catalan treatment plants, funded by the Catalan Water Agency and coordinated by the Catalan Institute for Water Research (ICRA). Another participant in this project is the Research Group on Virus, bacteria and protozoans of water interest in and food (VIRBAP) of the UB.