Fig. 1: colorimetric reverse transcription loop-mediated isothermal amplification (RT-LAMP) targeting N and E genes allows the detection of severe acute respiratory syndrome coronavirus (SARS-CoV-2) variant omicron. Selected nasopharyngeal swab-derived samples, previously detected positive for SARS-CoV-2 by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and identified as the new omicron variant of concern (VOC) by next generation sequencing, were included as input for colorimetric RT-LAMP reaction targeting N and E genes. RT-LAMP reactions were performed combining the primer sets N2/E1 in the same reaction (multiplex) or independently.⁽⁴⁾ Both strategies resulted in positive reaction as evidenced by yellow colour. Negative or absence of specific amplification is represented by pink colour and no bands on gel electrophoresis. RT-LAMP reaction was performed at 65ºC during 30 min, using the WarmStart^® colorimetric LAMP 2X master mix (NEB #M1804). RT-LAMP amplification products were resolved in 2% agarose gel and stained with GelRed^® (Biotium #41003) to confirm DNA amplification. +C: positive control using SARS-CoV-2 RNA extracted from laboratory-cultured inactivated SARS-CoV-2; NTC: non-template control. Upper panel cartoon is showing SARS-CoV-2 genome where N and E gene regions are zoomed in. Polymorphisms are indicated in their corresponding positions. The SNP C26270U, highlighted by the red arrow, is the only polymorphism that overlaps with F2 primer (magnifying glass). F3: forward; B3: backward; LF: loop forward; LB: loop backward; F2 and F1c: parts of FIP - forward internal primer; B1 and B2c: parts of BIP - backward inner primer. P: proline; L: leucine; R: arginine; K: lysine; G: glycine; S: serine; T: threonine; I: isoleucine; E: glutamic acid. BA.2, also known as 21L, is considered a sub-lineage of SARS-CoV-2 omicron. Genomic representation was created using SnapGene. Parts of this figure were created with BioRender.com and are licensed under the agreement number: QC23MCKTFE.