Background: In spite of the advances in the knowledge of the influenza A (H1N1) 2009 virus the efficiency of its transmission among close contacts, and the efficiency of non pharmacological interventions to reduce the attack rates AR is not well known. The goal of this study is to characterize the occurrence of confirmed influenza A (H1N1) 2009 virus outbreaks in school settings in Catalonia during the pandemic period and to assess the effectiveness of interventions carried out for their control.
Methods: Incidence of A (H1N1) 2009 outbreaks reported from may to December 2009 and their attack rates were calculated whether preventive recommendations were issued and interventions implemented. Variable associations were calculated by χ² test, means were compared by t-Student and proportions by the statistic z , statistical significance was established at α=0,05.
Results: In total 238 outbreaks were notified. The global attack rate was 15.5%. The AR was only available for 173 (72.7%) outbreaks, of which, 142 (82.1%; p<0.001) had an AR below 25%. The main area of transmission was the school, where 209 outbreaks occurred (88%; p<0.001), of which 187 (78.6%; p<0.001) corresponded to elementary-high school educational centers. There was significantly shorter mean duration of outbreaks depending on the emission of recommendations (p=0.04).
Conclusions: The assessment of influenza A(H1N1)2009 outbreaks presents supporting evidence of preventive measures and hygiene in the control of transmission in school settings.