While the inability to cultivate divergent HRV strains is a defining feature of the HRV A2s it is also a hindrance to classifying them. In our experience (data not shown), the earliest PCR-based methods [50] are already efficient at detecting these divergent strains. By extrapolating from published subgenomic sequence data, this clade is populated by a great number of divergent strains which are distributed both geographically and temporally, suggesting an endemic aspect to these previously uncharacterised viruses. No evidence exists to suggest that the HRV A2 strains are emerging viruses, rather it appears that they are newly identified strains that have been contributing to respiratory illness, in the absence of detection using culture-based diagnostic methods, for many years. There has now arisen a need for reliable protocols to characterise these putative viruses but in the absence of an HRV A2 isolate, neutralization, acid sensitivity and antiviral susceptibility studies, important for taxonomic placement, cannot be obtained. We have catalogued a series of features using methods which, while requiring further validation, contribute to our understanding of the biology and pathogenesis of HRV A2 strains. Additional molecular approaches will also be useful to classify other recently described divergent HRV strains [51] . Our data demonstrated that the newly identified HRVs, residing within the HRV A2 clade, do not satisfy the criteria for assignment to any existing HRV or HEV species and most likely constitute one or more novel species in the current genus Rhinovirus, tentatively called Human rhinovirus C (HRV C).