Comparisons of Clinical Features among Influenza A (H1N1) and Seasonal Influenza A and B during 2009 to 2010 at a Single Institution

Purpose: This study was performed to compare the clinical features of pediatric patients who were diagnosed with influenza A (H1N1) or seasonal influenza A and B during 2009 and 2010 at a single institution. Methods: Among children who visited the Dong-A University Hospital with fever (>37.8℃) and acute respiratory symptoms from September 2009 to February 2010, 1,004 children who were diagnosed with influenza A (H1N1) or seasonal influenza A and B by reverse transcription-polymerase chain reaction (RT-PCR) were enrolled. Monthly incidence, fever duration before diagnosis, symptoms (fever, cough, rhinorrhea, sore throat, headache, vomiting, abdominal pain, diarrhea, seizure, and dyspnea) and signs (rales, wheezing) were reviewed retrospectively in each group based on medical records. Results: Influenza A (H1N1) was detected in 944 patients (94.0%), followed by seasonal influenza A in 42 (4.2%) and seasonal influenza B in 8 (1.8%). The positive rate of influenza infection was highest in November 2009 (n=557, 55.5%). Mean duration of fever before RT-PCR was 1.6 days (range, 1.5 to 1.8 days). Except fever, cough was the most common symptom (n=792, 78.9%), followed by rhinorrhea in 407 patients (40.5%). Rales and wheezing were detected in 16 patients (1.6%) and 19 (1.9%), respectively. Significant differences were observed for the number of patients who had cough, headache, vomiting, and wheezing among the three groups (P<0.05). Conclusion: Although the incidence of cough, headache, vomiting, and wheezing differed significantly among the three groups, the number of patients in each group was too different to compare the results. (Pediatr Allergy Respir Dis(Korea) 2011;21:269-276)