Viruses causing lower respiratory symptoms in young children: findings from the ORChID birth cohort

Sarna, Mohinder; Lambert, Stephen B; Sloots, Theo P; Whiley, David M; Alsaleh, Asma; Mhango, Lebogang; Bialasiewicz, Seweryn; Wang, David; Nissen, Michael D; Grimwood, Keith; Ware, Robert S

Healthy children in the ORChID community-based birth cohort experienced an incidence rate of 978 new VDEs per 100 childyears during the first 2 years of life, with HRV playing a dominant role. Overall, respiratory viruses were detected by PCR in regular weekly swabs at least once during 75% of ARIs, while in asymptomatic periods 23% of weekly nasal swabs were positive by PCR for respiratory viruses, accounting for 33% of all new VDEs. We demonstrated evidence of attribution for ARIs by RNA viruses, which included HRV (HRV-A, HRV-C), influenza (IFV-A), parainfluenza (PIV-1, PIV-3), RSV (RSV-A, RSV-B), HCoV (HCoV-OC43, HCoV-NL63) and HMPV; and AdV as the single DNA virus representative. All these viruses were detected significantly more often in children with an ARI than during asymptomatic periods and had statistically significant positive AFEs. The largest association was observed for RSV and HMPV, both of which were more strongly associated with LRTIs than other respiratory viruses. Increasing age ≥6 months, non-summer months and childcare attendance were independent risk factors for symptomatic VDEs. Age as a host risk factor for symptomatic infection is also noted in other studies, 23 and is presumably due to protection afforded by maternal transplacental and breastmilk antibodies in the very young. 24 Environmental risk factors of season and childcare attendance for ARIs may be related to the intensity and opportunity for exposure in these settings experienced by young children. 10