Human rhinoviruses (HRVs), the agents of the common cold, are single-stranded, positive-sense RNA enteroviruses in the Picornaviridae family. They are classified primarily by capsid serotyping relative to a historical repository of 99 strains, obtained from clinical specimens. 88 of the major HRVs are classified by an intercellular adhesion molecule–1 (ICAM-1) and 11 minor viruses by a low-density lipoprotein receptor (LDLR) used for cell entry.  The genomic sequences of viral capsid-coding regions, non-coding regions, and a limited number of complete genomes have resulted in a division of the original 99 strains into two species: HRV-A (containing 74 serotypes) and HRV-B (containing 25 serotypes).