Impact of pandemic A/H1N1/2009 influenza on children and their families: comparison with seasonal A/H1N1 and A/H3N2 influenza viruses

Objectives: To make a direct comparison between the total burden of pandemic influenza and that of other seasonal influenza A viral subtypes in otherwise healthy children. Methods: The total clinical and socioeconomic burden of pandemic A/H1N1/2009 influenza was compared with that of seasonal influenza A viral subtypes in 389 otherwise healthy children with A/H1N1/2009, 126 with seasonal A/H1N1 and 486 with seasonal A/H3N2 infection referred to the Emergency Room and hospitalised in the in-patient units of a large, university-based paediatric hospital. Influenza diagnosis was confirmed by real-time polymerase chain reaction. Results: Regardless of age or gender, the variables significantly associated with pandemic A/H1N1/2009 and seasonal A/H3N2 infection were a diagnosis of lower respiratory tract infection upon clinical presentation, the need for hospitalisation, hospitalisation for 657 days, school absences of 657 days, the need for aerosol therapy, the household development of a disease similar to that of the infected child, and the need for additional household medical visits and antibiotic prescriptions (p < 0.001). A longer period of hospitalisation and lost school days seemed to be associated with pandemic A/H1N1/2009 infection (p < 0.01). Conclusions: Perceived symptom severity and the risk of serious outcomes are similar in children with influenza due to pandemic A/H1N1/2009 or seasonal A/H3N2 influenza, but both of these viruses seem to have a greater clinical and socioeconomic impact than seasonal A/H1N1 virus, regardless of the patients' age or gender