We filtered all genes based on statistically significant differential expression patterns identified by the likelihood ratio test for infection (adjusted P < 0.05), which produced 31 clusters of genes and coexpressed retroelements in Calu-3 cells, 13 clusters in A549 cells, and 18 clusters in A549-ACE2 cells (Figure 2 and Supplemental Figures 5–7). Here, ACE2 is linked to infection.