The restricted expression of FCGR3B in a comorbid gene set enriched severe COVID-19 cell type (Figure 3A) makes FCGR3B an interesting candidate marker gene for severe COVID-19, a notion that is further supported by the finding that FCGR3B was selectively expressed in severe cluster 11 compared with other FcR family genes (Figure 3C). Here, FCGR3B is linked to COVID-19.