Also reported in Italy. It has 28 peculiar mutations, 28 in common with BA.1. The data on contagiousness and lethality are still limited, also because it is not easy to identify it (it is necessary to sequence all the samples)
Under the lens of scientists and health authorities, the growth, in some European and Asian countries, of Omicron’s sister, the BA.2 lineage, which differs from BA.1 in some mutations (also in the Spike protein).
Where it is more widespread
In total, 40 countries uploaded more than 8,000 BA.2 sequences to Gisaid (the international portal of genomic data) as of November 17, 2021. Although it is not possible to determine where the sub-lineage may have originated, the first sequences were sent by South Africa and the Philippines and most of the samples were uploaded from Denmark (which is among the first countries in the world for sequencing capacity). Other countries with more than 100 samples are theIndia, Sweden and Singapore.
Because it is also called invisible
Omicron’s sister has also been called invisible because of difficult identification, since it does not have the deletion of the S gene characteristic of Omicron BA.1: to find it, therefore, all samples must be sequenced and this implies a laboratory capacity that not all countries have. The lack of the S gene, on the other hand, allows one to suspect the belonging of a sample to the Omicron variant of the classic type directly from the swab (without sequencing, which is done later).
The situation in Denmark, India and the UK
In Denmark BA.2 is spreading rapidly and by now prevalent with respect to BA.1. Anders Fomsgaard, virologist at the State Serum Institute Danish, said it now represents approx 65% of new cases. At the same time, he reassured: We are not so worried, since so far we do not see large differences in age distribution, vaccination status, reinfection and risk of hospitalization. Also, despite BA’s high infection rate. 2, the number of ICU admissions is decreasing, although the peak in Denmark has not been reached.
Similar growth rates of BA.2 are found in India compared to other variants (doubling every 4 days). In the country it became dominant towards the end of December.
In United Kingdom the Health Security Agency (UKHSA) designated the BA.2 sub-lineage as a variant under investigation on 21 January. The agency reports approximately 426 cases of Omicron BA.2 confirmed by the English Whole Genome Sequencing (WGS), with the first dated 6 December 2021. The areas with the highest number of confirmed cases are London and the South East. A British study reports an increase in new daily Covid symptomatic cases, which increased by about 10% in a week and hypothesizes a greater contagiousness of BA.2, all to be confirmed. All ‘Imperial College out of 1,816 positive samples analyzed, 99% were Omicron and 6 BA.2, the remaining 1% were Delta.
Also reported in Italy
In some countries a positive test with the S gene may still lead to suspicion of a Delta presence, but in England it is estimated that it is still more likely to have a BA.2 than a Delta, this is because Delta has long since been supplanted.
Also in Italy a minority Delta: according to the latest survey on the prevalence of variants published by the Istituto Superiore di Sanit on January 28th and referring to last January 17th, the Omicron variant 95.8% predominant, while Delta represents 4.2% of the sample examined. But BA.2 cases from our country have already been filed on Gisaid: 3 in Lombardy, 3 in Piedmont, 2 in Liguria and 1 in Campania.
Germany, South Africa and the USA
Omicron’s sister also grows up in Germansa, where more cases of BA.2 (5%) per day were detected on January 25 than in Delta (2-3%). BA.2 represents approx 30% of sequencing in Berlin, with a growth advantage over Delta of around 20% per day.
BA.2 also increasing in South Africa. At the end of November BA.2 accounted for approximately 2% of the Omicron cases detected, in the week from 10 January to 17 January it was 25%, in some provinces at 40%, but the growth for now is associated with a steady decrease in infections in the country.
BA.2 also spread throughout the Southeast Asia, less in the use, where it is still reported, even if very marginal.
For now it looks no different in effect
Currently, there is insufficient data to determine whether the BA.2 lineage is pi transmissible or has an immune evasion advantage with respect to the BA.1 lineage. Early observations from India and Denmark suggest that there is no difference in gravity.
BA.2 shares 32 mutations with BA.1, but also has 28 unique mutations. And in all, it has 70 more mutations than the native Wuhan strain, compared to BA.1’s 53.
Some analyzes suggest that Spike mutations have a fairly minimal impact on antigenicity compared to BA.1 and therefore the differences in the efficacy of vaccines against BA.2 compared to BA.1 are negligible.
The first studies fromImperial College they say thevaccine efficacy towards symptomatic cases preserved, indeed slightly higher for BA.2 than for BA.1.
It is also highly probable that BA.1 infection gives a fair amount of cross-reactivity against BA.2 infection.
The advantage of BA.2 compared to BA.1 estimated at around 10-15% in Denmark and 5-6% in Germany: in some countries the Omicron peak has been exceeded, so many scientists predict that BA.2 cannot cause other waves on its own (see the descent of cases in South Africa), could slowly replace BA.1 in the coming months, but i data on contagiousness and lethality are really limited (also considering the difficulty in intercepting the sub-variant), therefore it is necessary to continue to investigate.
January 28, 2022 (change January 28, 2022 | 16:43)
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