Human rhinovirus C: a newly discovered human rhinovirus species

Abstract

Although often ignored, human rhinoviruses (HRVs) are the most frequent causes of respiratory tract infections (RTIs). A group of closely related novel rhinoviruses have recently been discovered. Based on their unique phylogenetic position and distinct genomic features, they are classified as a separate species, HRV-C. After their discovery, HRV-C viruses have been detected in patients worldwide, with a reported prevalence of 1.4-30.9% among tested specimens. This suggests that the species contribute to a significant proportion of RTIs that were unrecognized in the past. HRV-C is also the predominant HRV species, often with a higher detection rate than that of the two previously known species, HRV-A and HRV-B. HRV-C infections appear to peak in fall or winter in most temperate or subtropical countries, but may predominate in the rainy season in the tropics. In children, HRV-C is often associated with upper RTIs, with asthma exacerbation and wheezing episodes being common complications. The virus has also been detected in children with bronchitis, bronchiolitis, pneumonia, otitis media, sinusitis and systemic infections complicated by pericarditis. As for adults, HRV-C has been associated with more severe disease such as pneumonia and exacerbation of chronic obstructive pulmonary disease. However, larger clinical studies with asymptomatic controls are required to better define the significance of HRV-C infection in the adult population. On the basis of VP4 sequence analysis, a potential distinct subgroup within HRV-C has also been identified, although more complete genome sequences are needed to better define the genetic diversity of HRV-C.

Figure 1

Phylogenetic tree of the VP4 region of HRV-C strains detected in different countries, showing the presence of a potential distinct subgroup. 201 nucleotide positions in each VP4 region were included in the analysis. The tree was constructed by a neighbor-joining method and bootstrap values were calculated from 1000 trees. The scale bar indicates the estimated number of substitutions per 50 nucleotides. Strains from Hong Kong are indicated by HRV-C/HK/strain no./year of detection. The GenBank accession numbers of the previously published sequences are as follows: HRV-QPM, EF186077; HRV89, A10937; HRV14, NC_001490; DK-1, EU697851; DK-30, EU697837; DK-33, EU697833; HC85215, EU697846; HC90837, EU697856; HC90841, EU697863; hRVLz118, EU822834; hRVLz123, EU822836; hRVLz127, EU822838; hRVLz144, EU822840; hRVLz148, EU822841; hRVLz163, EU822842; hRVLz167, EU822843; hRVLz185, EU822847; hRVLz269, EU822856; hRVLz333, EU822869; hRVLz383, EU822878; hRVLz390, EU822879; IN-26, EU697865; IN-35, EU697845; IN-36, EU697839; HRV 7316563, EU697850; NY-003, DQ875929; NY-028, DQ875931; NY-041, DQ875921; NY-042, DQ875926; NY-060, DQ875928; NY-063, DQ975924; SA365412, EU697852; SA440023, EU697829; SA442718, EU697828; SO4302, EU697869; SO4450, EU697835; SO4463, EU697854; SO4868, EU697854; NAT001, EF077252; NAT045, EF077253; NAT083, EF077264; QPID03-0035, EU155152; QPID03-0033, EU155153; QPID03-0028, EU155154; QPID04-0006, EU155158; HRVC 102307, EU687518; HRVC 102507, EU687523; HRVC 101507, EU687515; HRVC 120107, EU687527; HRVC102207, EU687516; HRVC 110507, EU687522; HRVC 103007, EU687519; HRVC 112007, EU687525; HRVC 103107, EU687520; HRVC 102107, EU687517; HRVC 111007, EU687524; HRVC 120407, EU687528; Pico tu304, EU081791; Pico tu306, EU081793; Pico tu403, EU081795; Pico 06-445, EU081796; Pico tu68b, EU081797; Pico g2-10, EU081798; Pico g2-11, EU081799; Pico 06-20, EU081800; Pico g2-12, EU081801; Pico g2-25, EU081802; Pico 06-447b, EU081806; Pico 06-230, EU081807; Pico 06-582, EU081809; Pico g2-3, EU081810; Pico 06-646, EU081811; Pico g2-8, EU081812; Pico 06-738, EU081813; Pico tu174, EU081814; Pico 06-225, EU081815.