The relation between influenza subtype and age, clinical symptoms, diagnosis, and clinical course was reviewed in hospitalised children in winter season annually since 2005 to 2014 respectively. The diagnosis of influenza was made by rapid diagnostic test kit or PCR test. The clinical features in each type of influenza were evaluated according to respiratory (R: pneumonia), neurological (N; seizure, abnormal behaviour), encephalopathy (E), and other symptoms (O;persistent fever, dehydration, gastroenteritis and others). The differential test for 2009 H1N1 was not performed in 2013–14 season.
Results 292 (180 boys, and 112 girls) cases were admitted due to influenza antigen positive disease in this study period. Seasonal type A was 128 (R; 45, N44, E;5, O;33), 2009 H1N1 was 95 (R:55, N;23, E;3, O;14), and type B was 69 (R;27, N;21, E;2, O;19) cases. 2009 H1N1 virus was detected only in2009–10 and 2010–11 seasons. The age distribution (0y/1–5y/6–10y/11y-) of these children was 26/64/32/6 in seasonal A, 10/24/40/21 in 2009 H1N1, and 1/33/29/6in type B. All children recovered and discharged without major complication. In respiratory disorder, percutaneous Oxygen saturation at admission was lower in 2009 H1N1 (median 88%) than seasonal A (96) or B (98), but total admission period was not longer.
Conclusion Rapid diagnostic kit is useful to know the origin of fever when patient should be admitted. The results support to understand the clinical picture of age related symptoms.