Two new sub-variants of Omicron

Two new sub-variants of Omicron, BA.4 and BA.5 are spreading rapidly and poised to outcompete past versions of the virus, extending the current COVID-19 surge.

International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b) on Tuesday said about the rapid spread of subvariant cases
Omicron BA.4 and BA.5 were first identified in South Africa in January and February 2022, respectively.

Limited data indicates that the newer sub-variants caused fewer hospitalisations and deaths compared to previous ones. As part of the countrywide COVID-19 testing network, icddr,b has been testing COVID-19 patients and monitoring SARS-CoV-2 variants.

The key findings are:
The Omicron variant in Bangladesh was first identified on 6 December 2021. Initially, the majority of COVID-19 positive cases were BA.1 (during the first two weeks of January 2022). The subvariant BA.2 emerged from the third week of January 2022, and circulated until the first week of April 2022 by replacing the BA.1 over time (Figure 1).

During 9 April to 13 May 2022, no sequencing was possible due to very low COVID-19 positivity rate and high Ct values of the positive samples.
The first suspected Omicron subvariant BA.5 in Dhaka was detected on 19 May 2022.

During the last six weeks (14 May to 24 June 2022), Omicron BA.5 became the most predominant subvariant. During this period, 51 out of 52 COVID-19 positive cases were identified as BA.5 subvariants and one BA.2 by using complete genome sequencing.

This report illustrates how SARS-CoV-2 variants are outcompeted one by another over time, which underscores the continuation of variant surveillance for a regular update on the emergence of new variants.