BA.2.12.1, BA.4, BA.5… What do we know about the new Omicron sublines?


New Covid-19 variants continue to multiply at varying rates in France and around the world. Enough to raise questions from scientists, some cases being considered “worrying”.

BA.2.12.1, BA.4, BA.5, XD, XE… New acronyms are appearing, as the Covid-19 virus continues to circulate in France and around the world, although the number of people hospitalized is down in France. While the BA.2 variant is currently the majority on French territory, Omicron sub-lines and recombinant variants have been detected in France and elsewhere in the world since the beginning of the year. Overview of these different strains and their characteristics.

• BA.4

Classified as a “variant of interest” by the World Health Organization (WHO), the BA.4 variant, from Omicron, was detected for the first time in South Africa last January-February, before be spotted in Botswana, Denmark, England and Scotland.

This variant is described as quite similar to another, BA.2, although its Spike protein has several additional mutations, one of which is of potential concern being described “as one of the factors associated to the significant transmissibility of the Delta variant”, according to Public Health France. Another area of ​​concern: The variant has been identified as a recombinant of Omicron with Omicron itself, according to Forbes. What give puzzles to researchers.

No certain transmission has been identified in Europe for the moment, but the BA.4 is the subject of “reinforced surveillance” in France, reports Public Health France. It remains considered “not of concern”, while only one case has been identified in France.

• BA.5

Also identified at the start of the year in South Africa, the BA.5 variant, also from Omicron, is considered a “variant of interest” by the WHO. Considered close to BA.2, it has mainly been detected in South Africa, as well as in Botswana so far.

Public Health France remains unconcerned despite everything, stressing that the BA.5 variant, like BA.4, is “not associated with a worrying epidemiological or clinical situation in South Africa where (the variants) circulate mainly”.

Two cases of BA.5 have been identified so far in France, according to Public Health France.

• BA.2.12.1

Cases are climbing in New York. The Omicron BA.2.12.1 variant has been spreading like wildfire in recent months in the United States, where it caused 29% of new national contaminations last week, and it has even become the majority variant in the Big Apple, according to Associated Press.

Highly present in the United States, the variant has also been detected in at least thirteen other countries, including Canada, Austria and Denmark. A case has also been identified in France.

According to the scientists, the variant would spread at an even greater speed than the BA.2 variant, which currently represents the majority of contaminations in France. Should we be alarmed? For the moment, the dangerousness remains a question mark, but, according to the latest figures, the number of hospitalizations is not experiencing particularly notable growth in New York.

• XE, XG, XH…: the recombinant variants of BA.1 and BA.2

Named XE, XG, XH, XJ, XL, or even XT, several recombinant variants have been sequenced in recent months mainly in Europe, such as the United Kingdom, Denmark, Finland, Germany, but also in Israel or even in India, according to The Practitioner’s Review.

Around 1,200 cases of XE were detected in the UK in particular in early April, according to a report by the UK Health Security Agency. Resulting from a combination between the BA.1 and BA.2 variants, the variant nevertheless remains an ultra-minority, representing less than 1% of the sequenced cases.

Close to the BA.2 variant, of which it possesses the majority of the genome, the XE variant would, on the other hand, have a growth rate 12.6% higher than that of BA.2, but this data is still being analyzed, the figure may be linked to a change in testing policy in the United Kingdom, according to British authorities.

Considered as belonging to Omicron, these variants have been detected at very low levels so far in France.

• XD delta-omicron

Around fifty cases of co-infection with delta and omicron variants have also been detected in France and a first case of the delta-omicron XD recombinant was sequenced in February, during a routine genomic surveillance Flash survey.

This recombinant brings together in its genome the sub-lineage of the Delta variant as well as the Omicron variant. 77 cases were reported in mid-April in France, but the variant remains rather stable, the majority of cases having been identified in family clusters, and has never exceeded more than 0.1% of detected cases.

More often associated with a loss of taste and smell than in the Omicron variant, no case contaminated with the XD variant was hospitalized in critical care.