Coronaviruses are enveloped, positive-sense RNA viruses with one of the largest genomes among RNA viruses (26 to 32 kilobases). Their genome is encapsulated and protected by a viral capsid that is composed of self-associating Nucleocapsid (N) protein. The N protein plays other important roles in coronavirus infectivity, including virus transcription and assembly.

One of the characteristic features of coronaviruses is crown-shaped spikes on the viral surface that are composed of the aptly-named Spike (S) protein. Coronaviruses gain entry into host cells through host receptor interactions with the S protein. Thus, the S protein is a major focus of drug development efforts to prevent and treat infections caused by coronaviruses.