MAFB and viral infectious disease: If, however, a low-level stimulation of TLR7 was present at steady state in at-risk patient groups, i.e., already prior to viral infection, the obese and elderly would be characterized by sentinel immune cells which are permissive to infection with SARS-CoV-2 because of endogenously high levels of miR-146a and detectable levels of MAFB.