Clinical manifestations of influenza A and B in children and adults at a tertiary hospital in Korea during the 2011-2012 season.

This study aims to evaluate and compare the epidemiological patterns and clinical courses of influenza A and B among children and adults. For this purpose, we retrospectively reviewed the medical records of 809 children and 271 adolescents/adults with laboratory-confirmed influenza between October 2011 and May 2012 at a tertiary-care hospital. Children with influenza B presented with high fever (body temperature >39℃), sputum production, diarrhea, nausea/vomiting, and myalgia more frequently than those with influenza A. Children with influenza B also showed longer intervals from symptom onset to the initiation of antivirals and higher rates of antibiotic prescription and hospitalization than those with influenza A. Adults aged 20-59 years accounted for approximately 16% and 20% of patients with influenza A and B, respectively. Although clinical manifestations and outcomes were similar between adult patients with influenza A and those with influenza B, influenza B may cause substantial disease burden among not only children but also socially active adults aged 20-59 years.