Quantitative detection of SARS-CoV-2 Omicron variant in wastewater through allele-specific RT-qPCR

On November 26, 2021, the World Health Organisation classified the B.1.1.529 SARS-CoV-2 variant as the Omicron variant of concern (VOC). Reports of higher transmissibility and potential immune evasion triggered flight bans and heightened health control measures across the world to stem its distribution. Wastewater-based surveillance has demonstrated to be a useful complement for community-based tracking of SARS-CoV-2 variants. Using design principles of our previous assays that detect VOCs (Alpha and Delta), here we report three allele-specific RT-qPCR assays that can quantitatively detect and discriminate the Omicron BA.1 and BA.2 variants in wastewater. The first assay targets the nine-nucleotide deletion at the L24-A27S of the spike protein for detection of BA.2. The second targets the six-nucleotide deletion at 69-70 of the spike protein for detection of the Omicron BA.1 variant, and the third targets the stretch of mutations from Q493R to Q498R for simultaneous detection of both Omicron BA.1 and BA.2. This method is open-sourced, can be implemented using commercially available RT-qPCR protocols, and would be an important tool for tracking the introduction and spread of the Omicron variants BA.1 and BA.2 in communities for informed public health responses.