Int J Infect Dis

BackgroundData on influenza illness rates with population denominators are needed to quantify overall morbidity and to prioritize public health intervention strategies.MethodsThe rates of influenza A(H1N1)pdm09 infection during pandemic phases were determined in a longitudinal community cohort study as part of an influenza vaccine study in a rural community of North India.ResultsDuring the 711 731 person-weeks of surveillance, a total of 1410/7571 (19%) febrile acute respiratory illness cases were positive for influenza. Of these, 749 (53%) were influenza A(H1N1)pdm09, 643 (46%) influenza B, and 18 (1%) influenza A (H3N2). The overall incidence rate of influenza-associated febrile acute respiratory illness was 128/1000 person-years. The incidence rates of influenza A(H1N1)pdm09 were high during both the pandemic phase (179/1000 person-years; November 2009 to January 2010) and post-pandemic phase (156/1000 person-years; August to October 2010), with children