ACE2 and COVID-19: Similar to the virus causing COVID-19 (SARS-CoV-2), HCoV-NL63 is the only seasonal coronavirus known to use the human angiotensin-converting enzyme 2 (ACE2) as cell penetration receptor, although studies suggest that the Spike (S) protein from HCoV-NL63 has a weaker interaction with human ACE2 than SARS-CoV-2 (12, 13).