Recent studies have generated 27 additional HRV A and 12 additional HRV B genomes [25, 26] also resulting in the proposal that individual HRV genomes are under purifying selective pressure and that significant intra-strain variation occurs only at the antigenic sites [26] . This is in stark contrast to the HEVs for which recombination in the non-structural regions is a significant contributor to viral diversification [27, 28] . Untypeable rhinoviruses have been described using PCR-based tools, since 1994 [29] but it was only in 2007 that the complete coding sequences of a number of novel and apparently divergent HRV strains were reported, permitting a for identification of the first new strains in two decades [30] . The initial strain described, HRV-QPM, was identified from children with presenting symptoms often suggesting bronchiolitis [31] . Subsequently, 'HRV-Xs' were found in an adult asthma study in the United States [32] and 'HRV-Cs' were described from a study of pediatric infection by human bocavirus in Hong Kong [33] . Some notable features associated with these six putative viruses include the reliance upon molecular methods for their detection, their apparent endeminicity, their failure to produce cytopathic effects in culture, their frequent detection in subjects with expiratory wheezing and their limited sequence identity with existing HRV strains but high shared sequence identity. Studies employing subgenomic sequences proposed that there were many of these putative viruses occupying a distinct position within the genus Rhinovirus, which we collectively called HRV A2 [34] . It has been proposed that these strains may constitute a new picornavirus species [33] . Data have not yet been presented which appropriately address classification using current ICTV criteria and the scope of the clinical impact of these divergent strains has not yet been studied in detail. Because it appears that the members of this clade are frequently associated with LRT illness we sought to better characterise them in the hope of finding features that might prove useful in predicting the outcome of HRV A2 infection.