While the discovery of HRV-Cs is recent, there are no indications that they are new viruses, or that they are emerging in real-time. Genetically, HRV-Cs are most closely related to the members of HRV-A and HRV-B but even a small genetic difference can impart encompass significant changes to their clinical impact, complicated by a diverse human background of prior virus exposure and underlying host immune and disease variability. It is well known that HRVs are a major trigger of asthma exacerbations and HRV-Cs are now under investigation for their potential involvement in asthma inception. The newly described HRV-Cs account for a large proportion of HRV-related illness, including common colds and wheezing exacerbations. HRV-Cs are genetically diverse and appear to circulate with seasonal variation, exchanging dominance with HRV-A. Whether HRV-Cs are consistently more pathogenic or "asthmagenic" is unproven. Antigenic diversity complicates passive and active prophylactic interventions (i.e. antibodies or vaccines), so further identification and characterisation of individual types (and their neutralising antigens) is likely to inform future preventive strategies. In the meantime, new antivirals should benefit groups at risk of the most severe disease.