Background: On May 19, 2009, 21 cases of influenza-like illness were reported among soldiers from an Engineering Military Academy (ACING) in Hoyo de Manzanares, Spain. In the context of an influenza A (H1N1)2009 global alert, it was decided to investigate a possible pandemic influenza outbreak. To describe a possible outbreak of influenza A (H1N1)2009 in a Military Training Centre and to describe the measures adopted for transmission control of this new infection.
Methods: A specific questionnaire was administered and biological samples were collected from all cases under investigation. Isolation and quarantine were recommended for cases and contacts, respectively.
Results: Eighty-one cases were confirmed. Among 52 samples tested, 31 were positive for influenza virus A/California/7/2009. The average age of the cases was 22.0 years (range 18-31 years) and 84% were men. Most common reported symptoms were cough and fever. All cases were isolated and treated with oseltamivir, with full recovery. The total attack rate was 12.42%. None of the cases had history of travel to risk areas or contact with previously diagnosed cases outside the academy. Thirty-one confirmed cases related to this outbreak were identified outside the academy, 24 cases were family contacts and friends.
Conclusions: This outbreak was the first evidence of community transmission of pandemic influenza H1N1 in Spain. The rapid detection of this outbreak enhanced an early implementation of measures aiming at the containment of its transmission.