National Center of Infectious and Parasitic Diseases, Sofia, Bulgaria

Announcement of the spread of SARS-CoV-2 variants in the country 04 February 2022

The National Center for Infectious and Parasitic Diseases (NCIPD) reports that 334 clinical samples with SARS-CoV-2 collected from 03-20 January 2022 were analyzed by next-generation whole-genome sequencing. The clinical samples were collected from 31 different medical centers, from 21 districts of the country.

249 (74.6%) of the samples were Omicron, including subvariants (BA.1, BA.1.1 and BA.2) and 85 (25.4%) were Delta (B.1.617.2) or Delta subvariants (AY.*). To define SARS-CoV-2 variants Nextclade v1.13.1 and Pangolin COVID-19 Lineage Assigner v3.1.17 programs were used. An epidemiological analysis is being carried out.

For the first time in Bulgaria, subvariants BA.2 of Omicron have been identified. Unlike BA.1, BA.2 lacks a 69-70 deletion in the S gene of the viral genome. This reflects in the results of the S-gene target failure (SGTF) screening tests with Real-time PCR as a proxy method to identify a probable Omicron variant, and in these tests the BA.2 variant may be misinterpreted as a non-Omicron.

According to the WHO, the presence of BA.2 is increasing in some countries.

For information on the classification of SARS-CoV-2 variants and sub-variants, please visit: https://cov-lineages.org/index.html

For an up-to-date classification of the variants of concern (VOC), please visit:

https://www.ecdc.europa.eu/en/covid-19/variants-concern

https://www.who.int/en/activities/tracking-SARS-CoV-2-variants/

The NCIPD continues to monitor the spread of SARS-CoV-2 in the country, with a focus on VOC, altered virulence and immunogenicity that are of increased public health importance.