For example, humanized mice expressing hACE2 under the epithelial cell-specific cytokeratin-18 (Krt 18) promoter (67), a universal chicken beta-actin (β-actin) promoter (68), or the human hepatocyte nuclear factor-3/forkhead homolog 4 (HFH4) promoter (25) are highly susceptible to SARS-CoV-2, develop severe pathological damage resembling COVID-19 symptoms in human lungs, and die rapidly. The gene discussed is ACTB; the disease is COVID-19.