The number of SARS-CoV-2 cases subjected to sequencing for virus variant determination is small. In contrast, specific PCR procedures are performed for most SARS-CoV-2 cases in Austria. Based on the detection of variant-specific mutations or wild-type gene expression, the viral variant can be determined with negligible uncertainty. To estimate the effective reproduction number, Reff, for the predominant variants, missing information on the virus variant must be imputed. Typically, Austrian laboratories initially test for the presence of the N501Y mutation. Thus, the information on the presence of the N501 virus type or the N501Y virus type is also the earliest available. According to Pangolin Nomenclature B.1.617.2, the delta variant, the currently predominant variant of concern (VoC) in Austria is an N501 VoC. Detection of N501 is already an early, albeit non-specific, indication of the likely presence of a delta variant. The evaluation was performed with data as of 07/21/2021. The effective reproductive number of the delta variant varies between 1.0 and 1.5 from 09/05/2021 to 07/19/2021, and for 07/19/2021 it is 1.34 (95% confidence interval: 1.29-1.39).

L. RICHTER ^(1,2), D. SCHMID ( ¹), E. STADLOBER ^{(2) 1} Department of Infection Epidemiology & Surveillance, AGES ² Institute of Statistics, Graz University of Technology.