TMPRSS2 and infection: In the small intestine, ACE2 expression ishigher in children. The ACE2 receptor acts as a gateway for thevirus and TMPRSS2 is used by SARS-CoV-2 to initiate the proteinspike, and NRP1, a SARS-CoV-2 coreceptor,increases the virus’s ability to enter and enhances infection inhost cells.