ABSTRACT
Influenza A(H1N1)pdm09 caused a deadly pandemic in 2009, replaced the seasonal influenza A(H1N1) virus that circulated prior to 2009, and still causes a serious infectious disease among children and adults [1]. In addition, Respiratory syncytial virus (RSV) infection remains a clinical burden on young children even though palivizumab has been effectively used for high-risk infants [2]. To compare the clinical impact of RSV infection with that of influenza in children, we retrospectively studied 2,375 children who presented to a hospital outpatient clinic between 2008 and 2010 with fever and/or symptoms of respiratory tract infection. The clinical aspects of RSV infection were compared with those of A(H1N1)pdm09 infection. After the influenza A(H1N1)pdm09 pandemic, 591 patients were diagnosed with influenza (Group 1), whereas 54 patients were diagnosed with RSV infection (Group 2). Before the pandemic, 203 patients were diagnosed with seasonal influenza (Group 3). All infections were diagnosed by using the rapid immunochromatography test, in which, prior to the pandemic, a positive test indicated seasonal influenza A(H1N1) exposure. However, during and after the pandemic, a positive test result suggested A(H1N1)pdm09 infection, which was confirmed by RT-PCR analysis of the sample and local etiological studies. In group 1, 31 children (average age 7.7 years, 5% of outpatients) required hospitalized for complications of the respiratory system (52%), central nervous system (16%), gastroenterological system (10%), and not specified (22%). In group 2, 33 children (average age 2.2 years, 60% of outpatients) were hospitalized, 27% of whom were administrated oxygen and 12% intravenous steroids. In group 3, 33 children (average age 6.8 years, 3% of outpatients) were hospitalized.