Letter to the Editor Markus Glaß, Laura Michaela Schian, Danny Misiak, Claudia Misiak, Simon Müller, Alexander Rausch, Katharina Angermann, Mariann Hoyer, Ramona Zabel, Ramyatha Battula, Astrid Kehlen, Beate Möbius, Jessica Weickert, Stefan Hüttelmaier and Matthias Karrasch* It did not stop there: rapid substitution of circulating SARS-CoV-2 variant of concern B.1.1.7 (Alpha) by variant of concern B.1.617.2 (Delta) and further evolution of different Delta sublineages in Southern Saxony-Anhalt in late summer 2021 https://doi.org/10.1515/labmed-2021-0168 Received November 10, 2021; accepted November 26, 2021; published online December 14, 2021 Keywords: SARS-CoV-2; surveillance; whole genome sequencing (WGS). To the Editor, In a recently published manuscript in the Journal of Laboratory Medicine [1], we reported about the estab- lishment of a regional SARS-CoV-2 surveillance program using whole genome sequencing (WGS) of SARS-CoV-2 isolates. Specimens were collected over a period of 5 months (January to May 2021) from patients suffering from COVID-19 and from outpatients without any clinical signs or symptoms. Sequence libraries were constructed from total RNA extracts using the Illumina COVIDSeq Test kit (Illumina, San Diego, US). During this time frame, the majority of the obtained sequences (252/364=69%) were assigned to the SARS-CoV-2 variant of concern (VOC) Alpha (B.1.1.7), and only very few other VOCs were found in our cohort [Beta (B.1.351, n=2); Delta (B.1.617.2, n=1)]. This situation rapidly changed throughout the sommer months of June to September 2021, in which VOC Delta (B.1.617.2 and sublineages AY.xx) rapidly became the dominant SARS-CoV-2 line- age in our study population within only one month (see Figure 1). In the months August and September 2021, a multitude of further Delta sublineages emerged (Figure 1). This spread of VOC Delta could also be observed when comparing SARS-CoV-2 genome se- quences from the entire country of Germany collected in the same time period, and submitted to GISAID (gisaid. org) [2]. A similar development was reported from other European countries [3, 4]. We have created interactive websites providing up-to-date SARS-CoV-2 lineage dis- tribution from our local area. All unfolding data deter- mined by our surveillance program are accessible via the URL https://ngs-info.medizin.uni-halle.de/shiny/SARS_ CoV2/SARS_CoV2.html. As already mentioned in our previously published manuscript [1], this fast changing situation further fosters the need for an established SARS-CoV-2 testing by WGS as an important surveillance tool for early detection of upcoming new lineages of concern [4, 5]. While in June all sequenced SARS-CoV-2 genomes from the study population were classified as B.1.1.7 (VoC Alpha), from July on only B.1.617.2 and its sublineages AY.xx (VoC Delta) were found. Stefan Hüttelmaier and Matthias Karrasch contributed equally to this work. *Corresponding author: Matthias Karrasch, MD, Department of Laboratory Medicine, Unit III, Halle University Hospital, Halle (Saale), Germany, E-mail: matthias.karrasch@uk-halle.de Markus Glaß, Laura Michaela Schian, Danny Misiak, Claudia Misiak, Simon Müller, Alexander Rausch and Stefan Hüttelmaier, Institute of Molecular Medicine, Section for Molecular Cell Biology, Charles Tanford Protein Centre, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany Katharina Angermann, A&A Praxis für Laboratoriumsmedizin und Med. Mikrobiologie, Halle (Saale), Germany Mariann Hoyer and Ramona Zabel, Amedes MVZ für Laboratoriumsdiagnostik und Mikrobiologie Halle/Leipzig GmbH, Halle (Saale), Germany Ramyatha Battula, Astrid Kehlen, Beate Möbius and Jessica Weickert, Department of Laboratory Medicine, Unit III, Molecular Diagnostic Section, Halle University Hospital, Halle (Saale), Germany J Lab Med 2022; 46(1): 77–78 Open Access. © 2021 Markus Glaß et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution 4.0 International License.