SARS-CoV-2 must bind to an ACE2 receptor, a protein present on the surface of cells in the mouth, lungs, heart, and other parts of the body, in order to enter a human body and start replicating. Researchers are concerned that the male testis, which has virtually the greatest amount of ACE2 mRNA expression among all body tissues, could be a target for viral invasion.
Male fertility because the SARS-CoV-1 virus, which caused the SARS outbreak in 2003–2004, had negative effects on male sexual organs and targeted the same ACE2 receptor. Numerous human viruses, such as Ebola, Zika, herpes simplex, Epstein-Barr, human papillomavirus, HIV, and mumps, have been linked to temporary or permanent problems with fertility, sex-transmission, and orchitis, a painful inflammation or swelling of the testicles.