CEACAM1 and COVID-19: Regarding the reliability of chronic conditions, although researchers are skeptical about using MHV-1 to study human COVID-19 due to the difference in receptors (ACE2 vs. CEACAM1), the severity, clinical, pathological, immunological, and functional features observed in MHV-1 more closely recapitulate changes seen in humans with SARS-CoV-2.