Pandemic influenza A (H1N1) in the North of Portugal: How did the Autumn-Winter wave behave? [Pandemia de gripe A (H1N1) no Norte de Portugal: Características da onda de Outono/Inverno]

Introduction: in april 2009 the centers for disease control and prevention announced the identification of a novel influenza virus in two patients in california,called influenza a (h1n1) 2009. on 11 june 2009 the director-general of the world health organization declared a pandemic of influenza a (h1n1). in portugal the first case of pandemic influenza a (h1n1) was reported on 29th april and the northern region of the country registered the first cases soon after that. aim: this report pretends to give an overview of the characteristics of autumn/winter pandemic wave in the north of portugal. results: a total of 64 195 cases of influenza-like illness were registered in public health services in the region between week 40,2009 and week 4,2010. the cumulative attack rate of those cases was 17.1/1 000 inhabitants. most of the cases occurred in females and in the under 20 years. the peak of the autumn/winter wave was attained in week 48,but geographic and time distribution of the pandemic was heterogeneous in the region. hospitalization rate for influenza- like illness cases in the population was higher for the under 10 years and decreased with age. forty four deaths in pandemic influenza a (h1n1) laboratory-confirmed cases occurred in the region (mortality rate - 1.2/100 000) and the risk of death was lower in younger age groups. the peak of deaths occurred two weeks latter than the peak of cases. conclusion: we can assume that the autumn/winter pandemic wave impact was mild in the northern region of portugal. we consider the importance of pursuing and reinforcing influenza surveillance in the region. © 2010 published by elsevier españa,s.l. on behalf of sociedade portuguesa de pneumologia. all rights reserved.