In this report, we looked for HRVs in a 2-year collection of NPSs from children with ARI visiting a district hospital in Shanghai, and found a high diversity of HRV strains that belonged to different species and genotypes. We characterized by RT-PCR and sequenced 66 HRVs, among them 27 HRV-A, five HRV-B, and 34 HRV-C strains. When sequencing the VP4/VP2 region of the HRV genome, several recent studies have identified new strains of viruses from children and adults with ARI, asthma, or otitis, which are clustered differently from HRV-A and HRV-B, and have been classified into a novel HRV-C species [7, 8, 17, 18, 19, 20, 21, 25, 26, 27, 28] . Other groups have also identified novel HRV-C strains by sequencing the VP1 gene [29] or the 59UTR [14, 15] . The different sizes and locations of the regions amplified in the HRV genomes renders difficult comparative genetic analysis. Recently, Palmenberg et al. (2009) have finalized the full-length genome sequences of all HRV-A and HRV-B reference strains, and identified structural features of these two species and the novel HRV-C species [16] . In our study, we identified 34 HRVs (51.5%) that clustered differently from HRV-A and HRV-B in a phylogenetic tree that was established on the basis of VP4/VP2 sequences, which were related to recent strains classified in the novel HRV-C species (Fig. 1, Table 2 ). Fourteen HRV-C strains (41.2%) segregated from the other 20 strains (58.8%) that were closely related to HRV-A in their 59UTR sequence (Fig. 2) . This led us to propose a classification of two HRV-C subspecies, HRV-Cc and HRV-Ca. In previous studies [15] . These strains clustered with our field strains within the HRV-Cc subspecies. Moreover, 17 strains that clustered with HRV-A, and had 12-35% pairwise nucleotide divergence from the nearest reference serotype [15] , clustered within the two major branches of HRV-A and HRV-Ca strains (Fig. 3) . Therefore, we cannot ensure that some of the 17 strains were HRV-A or HRV-Ca strains. Kiang et al. (2008) have identified five novel HRVs out of 24 clinical samples (20.8%), which segregated from HRV-A and HRV-B, and were classified as HRV-C, and three additional strains (12.5%) that also clustered with QPM, C024, C025, C026, NAT001 and NAT045 [14] (Fig. 2) . However, the field HRV strains of these previous studies were sequenced using a 59UTR that did not match fully our sequence and that of Lee et al. (2007) [15] , and could not be included in the present study for comparative analysis. Interestingly, the five strains identified in California in 2007 [14] and N42 and N45 from our study were closely related to strain W37 isolated in Wisconsin in the late 1990s [15] , and to NAT001 isolated in the winter of 2004 in California [18] , which confirms that similar genotypes of HRV-Ca are widespread [17] .