HRVs are grouped taxonomically into Human rhinovirus A (HRV-A) and Human rhinovirus B (HRV-B), 2 species within the family Picornaviridae (International Committee on Taxonomy of Viruses database [ICTVdb]; http:// phene.cpmc.columbia.edu). These nonenveloped, positivesense, single-stranded RNA viruses have been classifi ed serologically and on the basis of antiviral susceptibility profi le, nucleotide sequence relatedness, and receptor usage (2) . Phylogenetic analyses of viral protein VP4/VP2 and VP1 coding regions indicate the presence of 74 serotypes in genetic group A and 25 serotypes in genetic group B (2) .