[The 2009 pandemic influenza A (H1N1) virus infection: experience of a paediatric service at a third-level hospital in Lisbon, Portugal]

Introduction: The 2009 pandemic influenza A (H1N1) (i.e., Pandemic Influenza) is an acute, infectious illness caused by the influenza A (H1N1) 2009 virus. This disease involves respiratory, gastrointestinal and systemic symptoms along with a high incidence occurring at a paediatric age.

Objective: To study the epidemiology, approach and complications of Pandemic Influenza in the paediatric population of a third-level hospital in Lisbon, Portugal, between September and December 2009.

Materials and methods: A retrospective study of children who had received the influenza A (H1N1) 2009 virus test by real time reverse transcriptase-polymerase chain reaction (RT-PCR) were included. The following parameters were analysed: number of tests, days of illness, sex, outcome, age, symptoms, hospitalisation and reason for testing. The distribution and test results were compared with the Pandemic Influenza activity in Portugal. Moreover, among the confirmed cases of infection, the need for hospitalisation, risk factors, severity, chest radiography, treatment and complications were also examined.

Results: A total of 351 tests were performed, on average, 2.6 days after initial symptoms, which included 71.8% outpatients and 30% children younger than three years of age. Overall, 54.4% of the tests were positive for the influenza A (H1N1) 2009 virus and the main comorbidities were respiratory and cardiovascular in nature. One hundred ninety-one cases were confirmed by laboratory studies, and 13.6% required hospitalisation, which lasted an average of 2.7 days. In 82.2% of the cases, the severity was mild, with fever and cough as the most frequent symptoms at 91.9% and 93.7%, respectively. Therapy with the antiviral drug, oseltamivir, was implemented in 35.6% of the cases. Additionally, oseltamivir was used in twelve infants younger than one year in age, including a one-month-old infant with no observed side effects.

Discussion: The epidemiological data obtained are consistent with the published national and international studies. The scientific information available and the recommendations of the irectorate-General for Health contributed to the uniformity of the approaches and the successful outcome.