NKG2C+ NK cell expansions have also been observed following diverse viral infections in humans, including hantavirus infection, chikungunya virus infection, HIV-1 infection, and notably severe COVID-19 (Bjorkstrom et al. 2021, 2011; Guma et al. 2006; Maucourant et al. 2020; Petitdemange et al. 2011). This evidence concerns the gene KLRC2 and viral infectious disease.