[Clinical features of influenza A H1N1 2009: a multicentre study]

To describe clinical and epidemiological features of influenza A H1N1 2009 diagnosed patients in the Emergency Department of 4 hospitals.

Prospective multicentre study conducted from july to december 2009. The patients diagnosed by Real-Time PCR of influenza A H1N1 2009 in the emergency department were included. The test was requested according to the protocols established throughout the epidemic. Epidemiological, clinical, laboratory variables and outcomes were evaluated.

A total of 456 cases were included, with a median age of 6.5years (PC(25-75) 3-10.6). There were risk factors of complications In 266 patients (59.4%) due to the influenza, mainly: respiratory (47%), cardiovascular (17%), neurological (14%) and immunosuppression (11%). The most frequent symptoms were fever (96%), (88%) cough, (72%) rhinorrhoea, muscle aches or asthenia and breathing difficulties and, less common, gastrointestinal and neurological symptoms. Chest X-ray was performed on 224 cases (49%), with lobar (31%) and interstitial (15%) infiltrates. One hundred and forty patients (31%) were hospitalised and 3.2% required Intensive Care Unit (median stay 4 and 3.5days, respectively). The most frequent complications were pneumonias and bronchospasms. Three patients died (a previously healthy patient with myocarditis and 2 patients with encephalopathy due to respiratory failure). Another case of myocarditis recovered with sequelae.

The profile of patient with influenza A 2009 diagnosed in the emergency department was a school child, with risk factors of complications, presenting with respiratory symptoms and fever over a short time, and who can be discharged. It is important to emphasise myocarditis, as well as the usual respiratory complications of influenza virus.