According to a report issued on 13 July by the National Health Institute, Doctor Ricardo Jorge (INSA), this variant, associated to India and considered to be more transmissible, has a prevalence of 86.6 percent in Portugal, while the Alpha virus, initially identified in the United Kingdom, was only responsible for 10.2 percent of infections in the week of 28 June to 4 July.

INSA also said that the Delta variant already had a prevalence of 100 percent in the Lisbon and Tagus Valley regions and the Algarve, 88.2 in the North, 81.8 in the Centre, 95 percent in the Alentejo, 62.5 percent in the Azores and 79.2 percent in Madeira.

"Among other variants of interest circulating in Portugal, the variant/lineage B.1.621 stands out, detected initially in Colombia, which has shown a relative frequency of around 1 percent in recent weeks," says the study on the genetic diversity of the new coronavirus in Portugal.

According to the document, this "variant of interest" presents several mutations in the `spike' protein that are shared with some "variants of concern".

The World Health Organisation (WHO) classifies the virus variants as of "concern" (VOC) or of "interest" (VOI), having assigned, at the end of May, the designation of letters of the Greek alphabet to facilitate understanding.

In the VOC category are Alpha, first detected in the United Kingdom in December 2020, Beta, associated with South Africa since December 2020, Gamma, identified in Brazil in January 2021, and Delta, originating in India and classified as of concern in May this year.

The INSA report also indicates that the relative frequency of Beta and Gamma variants, initially associated with South Africa and Brazil, respectively, remains low and without an increasing trend, being less than 1 percent in the latest national samples.

Furthermore, no new cases of the Lambda variant, which has strong circulation in regions of Peru and Chile, were detected, the institute said.

As part of the study started in April 2020 on the genetic diversity of SARS-CoV-2, 11,386 sequences of the genome of the new coronavirus were analysed, obtained from samples collected in over 100 laboratories, hospitals and institutions, representing 290 municipalities in Portugal.

In June, the institute announced a reinforcement of the surveillance of Covid-19 virus variants circulating in Portugal, through its continuous monitoring.

This new strategy allows for a better genetic characterisation of SARS-CoV-2, as data will be analysed continuously, and there will no longer be time intervals between analyses, which were essentially dedicated to specific genetic characterisation studies requested by public health.