Prevalence of and risk factors for human rhinovirus infection in healthy aboriginal and non-aboriginal Western Australian children.

Acute lower respiratory infections are the leading cause of serious childhood morbidity and mortality worldwide, accounting for an estimated 11–20 million hospitalizations and 2 million deaths each year in children <5 years of age.1,2 In Australia, aboriginal children bear a disproportionate burden of acute lower respiratory infections compared with non-aboriginal children.3–6 As many as 19 viral pathogens have been associated with respiratory infections.7 Of these, human rhinoviruses (HRV) are the most common worldwide and are responsible for approximately two-thirds of cases of the common cold.8 More recently, HRVs have been shown to infect the lower respiratory tract9 and are the major upper and lower respiratory pathogens in the first year of life.10 HRVs were first discovered in 1956 and were originally classified into 2 distinct species, human rhinoviruses species a (HRV-A) and human rhinoviruses species B (HRV-B), comprising 101 serotypes identified using traditional serologic and cell culture methods.11–13 Recent advances in the molecular detection and typing of respiratory viruses led to the identification of a third species, human rhinoviruses species C (HRV-C), which was first reported in 2006.14 Since then, over 50 new genotypes have been identified15 but cannot be formally assigned into separate serotypes as they have not yet been cultured in vitro. However, a proposed genotyping scheme has recently been published that incorporates sequence-based typing.16 Several studies worldwide investigating the prevalence of HRV species in children hospitalized with an acute lower respiratory infections have reported higher detection rates of HRV-C than HRV-A or HRV-B.14,17–22 HRV-C has been associated with more frequent and severe respiratory illness than HRV-A or HRV-B.20,22 respiratory viruses, including HRV, are often detected not only in symptomatic but also in asymptomatic individuals.23,24 to date, little is known about the prevalence of HRV-C in healthy children living in the community. In the only study describing the prevalence of HRV-C in a control group of healthy children, 21 HRV-positive specimens were typed, of which 29% were HRV-C.23 this lack of information limits the ability to determine the causal role of HRV-C in childhood respiratory illness. The risk factors associated with the detection of HRV in the upper respiratory tract are not well understood. Day-care attendance and presence of siblings have been associated with HRV-induced wheezing among high-risk infants of atopic parents.25 However, little is known about the demographic, environmental and socioeconomic risk factors associated with detection of HRV or HRV species in healthy children. The Kalgoorlie Otitis Media research Project (KOMrP) aimed to investigate the causal pathways to otitis media in aboriginal and non-aboriginal children26 and provides the opportunity to study the epidemiology of HRV in healthy children. We have previously reported on the presence of respiratory viruses and bacteria that were identified in 1006 nasopharyngeal aspirates (nPas) from 79 aboriginal and 88 non-aboriginal children who had had at least 4 specimens collected before 2 years of age.24,27 HRV was the most frequently identified virus and was identified more often in aboriginal than in non-aboriginal children (24% versus 17%). HRV detection was also associated with the carriage of Haemophilus influenzae and Moraxella catarrhalis in aboriginal children. The prevalence of HRV species in aboriginal and non-aboriginal children and the risk factors associated with each species are unknown. We hypothesized that HRV-C would be less common than HRV-A among healthy children and that HRV detection would be positively associated with risk factors that may increase HRV transmission. Using a molecular method to type HRVs, we aimed to describe the prevalence of HRV species in specimens collected from healthy aboriginal and non-aboriginal children and their associations with potential demographic, environmental and socioeconomic risk factors. We also aimed to describe the associations between HRV species and concurrent carriage of respiratory bacterial pathogens.