Some papers propose that this may be due to a different expression of angiotensin-converting enzyme 2 (ACE-2) or transmembrane protease serine 2 (TMPRSS2) receptors, or to lower production of proinflammatory cytokines such as interleukin-6 (IL-6) in women after a viral infection (44, 45). Here, TMPRSS2 is linked to viral infectious disease.