Line BA.2 ″clearly dominant″ and responsible for 76.2% of infections

The BA.2 lineage of the omicron variant of the SARS-CoV-2 coronavirus, considered more transmissible, is “clearly dominant” in Portugal and already represents 76.2% of infections, announced the National Institute of Health Doutor Ricardo Jorge (INSA).

“It is estimated that the BA.2 lineage is already clearly dominant in Portugal, representing 76.2% of positive samples on March 7”, says the INSA report on the genetic diversity of the coronavirus that causes the disease covid-19. .

According to INSA, this strain was detected for the first time in Portugal in random sampling by sequencing in the week between December 27, 2021 and January 2 and, since then, its “frequency has gradually increased”.

The omicron variant, classified by the World Health Organization (WHO) as of concern, encompasses several lineages identified by the prefix BA, including BA.1 and BA.2, which descend from the same ancestral lineage (B.1.1.529). ) and have an “excess” of mutations in the `spike´ protein, many of which are shared.

According to the sequencing data, the BA.1 lineage reached a maximum prevalence of 95.6% in the week of January 10 to 16, when it started a downward trend, with INSA estimating that on Monday it will be responsible for only 23.8% of infections.

Recently, the WHO advanced that “preliminary studies suggest that BA.2 appears to be more transmissible than BA.1”, but the organization notes that “real world” data on clinical severity in South Africa, UK and Denmark, where immunity from vaccination and natural infection is high, indicate that “there was no reported difference in severity between BA.2 and BA.1”.

“Reinfection with BA.2 following infection with BA.1 has been documented, but initial data from population-level studies suggest that infection with BA.1 provides strong protection against reinfection with BA.2.” WHO.

As part of the continuous monitoring of the genetic diversity of SARS-CoV-2 that INSA is developing, an average of 523 sequences have been analyzed per week since the beginning of June 2021, from samples collected randomly in laboratories distributed throughout the 18 districts. mainland Portugal and the autonomous regions of the Azores and Madeira, covering an average of 139 municipalities per week.