The identification of viruses with furin cleavage site deletions in clinical samples from COVID-19 patients16,17 and the differential infectivity and replication of the WT and BriSΔ viruses suggests that in the heterogenous environment of the human body, SARS-CoV-2 variants with abrogated S1/S2 cleavage replicate preferentially in specific cell types. This evidence concerns the gene FURIN and COVID-19.