Burden of severe 2009 pandemic influenza A (H1N1) infection in children in Southeast Spain.

Introduction: Most of the published studies on patients admitted with 2009 pandemic influenza are not population based. We have compiled the clinical information regarding all children admitted with 2009 pandemic influenza A (H1N1) infection during the season 2009-2010 in our defined population, in order to have an unbiased view of the most severe side of the clinical spectrum of the infection and to quantify its burden.

Methods: Children <15 years-old admitted to any of 3 hospitals in South-East Spain with 2009 pandemic influenza A (H1N1) detected by means of reverse transcriptase polymerase chain reaction. High quality data were extracted from clinical records specially designed for the pandemic.

Results: Eighty two children fulfilled the inclusion criteria. The hospitalization rate was 68 per 100,000 children <15 years-old; in those <5 years-old the rate was of 131 and in <1 year-old, 234 per 100,000. An estimated 0.7% of the children who suffered from pandemic influenza were admitted (1.7% in <5 years-old). Intensive care was required for 5% of the hospitalized patients living in the study area. Mortality was roughly estimated about 1 per 100,000 children <15 years-old and was associated with the presence of very severe comorbidities or co-infections. Only 20% of the admitted children were ≥ 5 years-old and without risk factors. The disease followed a generally benign course despite the modest use of oseltamivir (49% of the patients).

Conclusions: Clinical and epidemiological data are very similar to those observed in other places and in interpandemic seasons with a high influenza activity.