Comparative analysis of clinical characteristics of pandemic influenza a/h1n1 and seasonal influenza a infections in hospitalized children.

Pandemic influenza A/H1N1 (piA) caused significant morbidity and mortality worldwide. We compared characteristics of piA (2009/2010) to those of seasonal influenza A (2007/2008/2009) in 134 (piA/seasonal influenza A: N = 55/79) hospitalized patients <18 years of age. Chronic disease was present in 25%/33%. Most common symptoms were fever (87%/94%), cough (78%/86%), rhinitis (76%/76%) and pharyngitis (67%/68%). Croup syndrome (15%/3%), conjunctivitis (31%/10%) and febrile seizures (26%/13%) were more frequent in piA; 64%/53% patients had ≥1 complication, and 5 (3/2) were admitted to intensive care unit. Oseltamivir use was 20%/0%. Severity of pandemic influenza disease was not different compared with seasonal influenza A in preceding years.