In the cycle of infection for most virus, the first step is to attach to the surface and recognize cell surface receptor of the host cell for invasion.15,16 With similar external subdomain of receptor-binding domain (RBD), 2019-nCoV spike share same host-cell receptor—angiotensin-converting enzyme II (ACE2)—with SARS-CoV spike, but in a higher affinity than SARS-CoV spike.17–21 In another word, cells expressing cell surface receptor ACE2 are susceptible to 2019-nCoV, similar to SARS-CoV. This evidence concerns the gene ACE2 and infection.