ACE2 and infection: Infection with the Omicron variant caused limited bodyweight loss, lower viral load in the upper and lower respiratory tracts, and limited lung pathological damage and mortality rates compared with earlier variants in both hamsters or human ACE2 (hACE2) transgenic mice.32,52,53 In addition, the Omicron variant was less effective in antagonizing cellular interferon signaling compared with the Delta variant.