The start of the epidemic in Portugal was marked by the “massive dissemination” of a variant of SARS-CoV-2 with a specific mutation, which began to circulate in the North and Central regions more than a week before diagnosis of the first cases.

This conclusion is part of the "Study of the genetic diversity of the new SARS-CoV-2 coronavirus in Portugal", released today at the DGS regular press conference to update information about the pandemic in Portugal, a research project coordinated by the National Institute of Health Dr. Ricardo Jorge (INSA), to analyse the genetic diversity of the new coronavirus, which causes the covid-19 disease, especially during the first months of the epidemic.

The first results of the study, which has already analysed 1,785 sequences of the genome of the new coronavirus, reveal that “the beginning of the pandemic in Portugal was characterised by the massive dissemination of a variant of SARS-CoV-2 with a specific mutation in the protein 'Spike'” , which has been the subject of research and the main focus of the vaccine for being responsible for binding the virus to human cells, allowing infection.

This “D839Y” variant of SARS-CoV-2 will have entered Portugal, in the North and Centre, “around February 20, associated with travel to Italy, specifically to the region of Lombardy”, the coordinator of the research, João Paulo Gomes.

"It will have circulated in a little uncontrolled way, or at least undetected in these areas of the country, and will have caused massive spread and a series of transmission chains before the first cases were reported in Portugal," said the coordinator of the study.

The first cases of covid-19 were reported on March 2, one associated with Hospital de Santo António and another with Hospital de São João, in Porto, but they are not linked to the “D839Y”.

"So this started long before, we have no doubt," said the INSA investigator.

The most notorious example of its spread was the outbreak in the municipality of Ovar, where the implementation of a sanitary fence would have prevented its spread to other areas of the country.

“During the exponential phase of the pandemic in Portugal, which was basically in March and in the first days of April, it [the variant] reached 33% of the cases on certain days, 3% of all cases had this mutation, and in cumulative data, we calculated that on April 9 or 10, this mutation was present in about 4,000 people with covid-19 ”, he stressed.

For the researcher, this can be "a great model" to understand how it all started, how the infection spreads and "how important are some measures taken at the right time".

He also considered that if the measures had “been a little anticipated, they would have worked even better”, but at the time there was no data to justify them.

“Now, with these models and with these results, we know that, in fact, a few days before, many transmission chains, many hospitalizations, many infections in general would have been avoided”.

For the researcher, "this type of retrospective analysis, carried out on an unprecedented scale in Portugal, can be used as a 'trump card' for combat in future situations, whether in a second wave of covid-19, or in other possible epidemics".

"Its conclusions will serve above all as a lesson for us to prepare for a near or distant future, it does not mean that they are of immediate application", said João Paulo Gomes at the press conference.

"It will be very important for all of us to understand exactly how we got to where we got to and to what extent public health measures were timely and effective," he said.

The study, funded under the first edition of the Research4Covid support program, has the participation of more than 60 hospitals / laboratories across the country.