The NCIPD has successfully analyzed 94 clinical samples with SARS-CoV-2 by next-generation whole genome sequencing. The samples were collected from patients with COVID-19 between 24.08-14.09.2022 and were sent from 13 different medical institutions in 13 districts of the country.

A recombinant variant between Omicron subvariants BA.5.1 and BA.2, which is designated “XAN”, has been identified for the first time in Bulgaria.

Recombinant viruses occur when a person is infected at the same time by two different viruses that have similar genetic material. As the two sub-variants replicate rapidly in the cells of their human hosts, they can swap some of their genetic material and form a new “hybrid” sub-variant made up of the two parent viruses.

XAN is still rare in the world; in Bulgaria it was found in a 76-year-old woman who was successfully cured.

The Omicron variant was detected in all 94 clinical samples and the proportion was as follows: BA.2.75 (1.1%), BA.2.12.1 (1.1%), BA.5.x (77.7%), BE.x/BF.x, which is a sub-variant of BA.5 (19.1%) and XAN (1.1%).
Pangolin COVID-19 Lineage Assigner v4.1.1. program was used to define SARS-CoV-2 variants. An epidemiological analysis is being carried out.

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.