TMPRSS2 and infection: In this study, the selected host genes (ACE2, ANPEP, DPP4 and TMPRSS2) are well known to be involved in the infection mechanisms of coronaviruses: three of them encode for receptors of a few viruses of this group and another one encodes for a key proteinase involved in the initiation of the infection after the invasion of the host susceptible cells32–43.