Abstract
BACKGROUND: Influenza infection can result in severe disease with debilitating complications. Young children have the highest rate of influenza hospitalisations with various factors influencing influenza susceptibility and severity. OBJECTIVES: This study aimed to determine the disease burden and assess risk factors for severe hospitalised influenza in South Australian children under 5 years of age. METHODS: Influenza admissions to the tertiary paediatric hospital in South Australia from 2008 to 2012 were identified. Data from laboratory-confirmed influenza cases were collected, including infecting influenza strain, co-infections, prematurity, pre-existing medical comorbidities and other potential risk factors. Predictors of high-level care were assessed using logistic regression. RESULTS: A total of 267 children with laboratory-confirmed influenza were hospitalised. Of these, 147 admissions (53%) occurred in children without underlying medical risk factors. Eighteen children (7%) required high-level care, of which 11 (61%) had no underlying medical risk factors. No deaths were reported. The majority of children were unimmunised against influenza. Co-infections were identified in 40% of children (n = 107). Influenza B was associated with a requirement for higher care (OR 3.7, CI 1.3-10.9, P = .02) as was a history of food allergies (OR 9.7, CI 1.5-61.4, P = .02) and iron deficiency anaemia (OR 4.8, CI 1.4-16.1, P = .01). CONCLUSIONS: Influenza can be a severe illness, even in children without underlying medical conditions. The identification of Influenza B strain, history of food allergies and iron deficiency anaemia as predictors of severity in hospitalised cases warrants further investigation and may have important implications for preventative strategies to reduce the burden of childhood influenza.