We report 25 cases of infection with SARS-CoV-2 Omicron variant containing spike protein L452R mutation in northern Lombardy, Italy. Prevalence of this variant was >30% in this region, compared with <0.5% worldwide. Many laboratories are using previously developed L452R-specific PCRs to discriminate Omicron from Delta mutations, but these tests may be unreliable.
Keywords: COVID-19; Italy; SARS-CoV-2; SARS-CoV-2 Omicron variant; coronavirus disease; respiratory infections; severe acute respiratory syndrome coronavirus 2; viruses; zoonoses.