easonality of respiratory viral identification varies with age and Aboriginality in metropolitan Western Australia

BACKGROUND: Viral respiratory infections are a major cause of pediatric illness. It is not known whether seasonality of viruses differs between Aboriginal and non-Aboriginal children of varying ages. METHODS: We extracted data on respiratory syncytial virus (RSV), influenza viruses A and B, parainfluenza virus types 1, 2, and 3 and adenovirus identified through cell culture or direct immunofluorescence between 1997 and 2005 from nasopharyngeal or throat specimens at Western Australia's only pediatric hospital. We used harmonic analysis in generalized linear models to examine the variations in seasonality of these viruses with Aboriginality and age. RESULTS: A respiratory virus was identified in 32% of 32 741 specimens. RSV (18.6%), influenza virus A (5.1%), and parainfluenza virus 3 (4.0%) were most common. The median age at time of identification was lower in Aboriginal children than non-Aboriginal for all viruses except RSV. Seasonality differed between all viruses and varied with age for RSV, influenza viruses and adenovirus. Influenza viruses A and B activity peaked earlier in Aboriginal than non-Aboriginal children during 1997, 1998, and 2002. CONCLUSIONS: All viruses showed distinct seasonality. Variability with age and different seasonal patterns for influenza viruses in Aboriginal children compared with non-Aboriginal children has to be taken into account when identifying target groups and timing for vaccination and other interventions.