SARS-CoV-2 Variants in Dhaka City: Emergence of Omicron BA.5 Subvariant

Newer iterations of the Omicron variant, BA.4 and BA.5 are spreading rapidly and poised to outcompete past versions of the virus, extending the current COVID-19 surge. Omicron BA.4 and BA.5 were first identified in South Africa in January and February 2022, respectively. Limited data indicate that the newer subvariants 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.


Figure 1: Weekly distribution of circulating SARS-CoV-2 variants in Dhaka city from 1 Jan 2021 to 24 June 2022. The bar graph (Y-axis) indicates the % of variants identified, and numbers are printed inside.

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.

Clinical data and vaccination history were available for 40 Omicron BA.5 infected patients. The findings are given below.

  • Male 16, Female 24
  • 39 patients had mild to moderate symptoms, and one had no symptom
  • Only one was hospitalised for one day
  • 11 were re-infected for the 2nd time and seven for the 3rd time
  • 38 patients had received at least one dose vaccine. Among them, 16 had received booster doses of vaccines, 21 had two doses, and one had received only one dose.
  • None had travel history.

Overall, the severity of the disease caused by Omicron BA.5 subvariant among our study population is low. However, the recent countrywide upsurge of COVID-19 cases as well as hospitalisation warrants continuation of public health and social measures to minimize the transmission of the virus.

Therefore, everyone should practice the following precautions to keep safe from COVID-19

  • Vaccination is key, get vaccinated.
  • Keep wearing well-fitted facemask
  • Maintain physical distancing, even though vaccinated or naturally infected.
  • Wash hands with soap and water frequently.