GZMK and viral infectious disease: Further unbiased investigation into the most expressed genes per cluster revealed a plethora of genes previously reported in the context of viral infections, such as Il7r, Tcf7, Zeb2, Klrg1, Gzma, Gzmb, Gzmk, Vim, Lgals3, Tox, Lag3, Pdc1, Id3 (Figure 1B and Supplementary Figures S2, S3, S4).