KRT18 and infection: We were also able to confirm SARS-CoV-2 viral presence in hCD147KI-NSG, hACE2KI-NSG, and K18-hACE2-B6 mice in a subsequent experiment by sm-FISH microscopy (Additional file 1: Figure S5) compared to infected WT-NSG mice 48 h after infection demonstrating higher susceptibility of these knock-in and transgenic strains to viral infection during the early infection phase.