By 4 DPI, the majority of K18 hACE2 transgenic mice had 25% or greater lung involvement indicative of pneumonia (Fig. 5g), with affected areas presenting with inflammatory cellular accumulations and hemorrhage in alveolar spaces (Fig. 5h, asterisk) and interstitium (Fig. 5h, bracket), intra-alveolar fibrin admixed cellular debris (Fig. 5h, arrow), vasculitis (Fig. 5h, bracket), edema (Fig. 5h, arrowhead), and neutrophilic rhinitis (Fig. 5o, bracket). This evidence concerns the gene KRT18 and susceptibility to pneumonia measurement.