Seasonality of respiratory viral identification varies with age and aboriginality in metropolitan Western Australia

Background: Viral respiratory infections are a major cause of pediatricillness. It is not known whether seasonality of viruses differs betweenAboriginal and non-Aboriginal children of varying ages.Methods: We extracted data on respiratory syncytial virus (RSV), influenzaviruses A and B, parainfluenza virus types 1, 2, and 3 and adenovirusidentified through cell culture or direct immunofluorescence between 1997and 2005 from nasopharyngeal or throat specimens at Western Australia’sonly pediatric hospital. We used harmonic analysis in generalized linearmodels to examine the variations in seasonality of these viruses withAboriginality 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 inAboriginal 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 peakedearlier in Aboriginal than non-Aboriginal children during 1997, 1998, and2002.Conclusions: All viruses showed distinct seasonality. Variability withage and different seasonal patterns for influenza viruses in Aboriginalchildren compared with non-Aboriginal children has to be taken intoaccount when identifying target groups and timing for vaccination andother interventions.