In addition to protein membrane receptors, infection of host cells by HCoVs also relies on sialic acid-containing glycoproteins and gangliosides, which are used by a broad range of viruses as receptors, such as influenza [20] and HCoVs including SARS-CoV [21] and HCoV-OC43 [13,22,23]. A recent molecular structure analysis showed that SARS-CoV-2 not only uses ACE2 as a receptor, but also recognizes highly conserved gangliosides on the host cell surface through sialic acid [24,25]. CQ/HCQ binds sialic acids and gangliosides with high affinity, which can prevent the attachment of SARSCoV-2 S protein to gangliosides [25]. CQ had inhibitory effect on quinone reductase 2 (QR2) involved in the biosynthesis of sialic acids [26,27]. Hence, the mechanism of anti-CoV activity of CQ/HCQ may also be related to hindering the recognition process of sialic acid and ganglioside (Figure 1).