CX3CR1 and COVID-19: In both our A/H7N9 (Fig. 8a) and COVID-19 (Fig. 8b) datasets, IL18R1 expression inversely correlated with expression of GZMA, GZMB, PRF1 (Perforin 1), EOMES, KLRG1 and CX3CR1. As IL18R1 expression in humans (Fig. 1c-e, Fig. 2, Fig. 3) and mice (Fig. 4b) is associated with disease severity, it was not surprising that GZMA, GZMB, PRF1, EOMES, KLRG1 and CX3CR1 gene expression decreased with disease severity (Fig. 8a, b).