KIR3DL1 and viral infectious disease: The presence of this variant KIR gene profile (KIR2DL2+/KIR2DS2-) in the group of severely ill SARS-CoV-2 patients leads to the hypothesis that the presence of KIR2DL2 and the absence of KIR2DS2 determine a lower efficiency of NK cell-mediated defense against viral infection which consequently increases the risk of serious clinical manifestations.