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Pandemic and post-pandemic Influenza A (H1N1) infection in critically ill patients

Ignacio Martin-Loeches12*, Emili Díaz2, Loreto Vidaur3, Antoni Torres4, Cesar Laborda5, Rosa Granada6, Juan Bonastre7, Mar Martín8, Josu Insausti9, Angel Arenzana10, Jose Eugenio Guerrero11, Ines Navarrete12, Jesus Bermejo-Martin13, David Suarez14, Alejandro Rodriguez2 and the H1N1 SEMICYUC/REIPI/CIBERES Working group

Author Affiliations

1 Critical Care Center, Parc Taulí Hospital-Sabadell, CIBERes, Sabadell, Spain

2 Critical Care Department, Hospital Joan XXIII/CIBERES/IISPV/URV- Tarragona, Spain

3 Critical Care Department, Hospital Donostia/CIBERES - San Sebastian, Spain

4 Pneumology Department, Hospital Clínic of Barcelona, IDIBAPS, Centro de Investigación Biomédica en Red-Enfermedades Respiratorias (CIBERES, CB06/06/0028), University of Barcelona, Barcelona, Spain

5 Critical Care Department. Hospital Vall d'Hebron/CIBERES/IRVH - Barcelona, Spain

6 Critical Care Department, Hospital de Bellvitge/CIBERES - Barcelona, Spain

7 Critical Care Department, Hospital La Fe -Valencia, Spain

8 Critical Care Department, Hospital La Candelaria - Tenerife, Spain

9 Critical Care Department, Hospital de Navarra - Pamplona, Spain

10 Critical Care Department, Hospital V. de la Macarena/CIBERES - Sevilla, Spain

11 Critical Care Department, Hospital G.Marañón/CIBERES - Madrid, Spain

12 Critical Care Department, Hospital V. de las Nieves - Granada, Spain

13 Infection and Immunity Unit, Hospital Clínico Universitario-IECSCYL, Valladolid, Spain

14 Epidemiology and Assessment Unit, Fundació Parc Tauli, Universitat Autònoma de Barcelona, Sabadell, Spain

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Critical Care 2011, 15:R286  doi:10.1186/cc10573

Published: 28 November 2011



There is a vast amount of information published regarding the impact of 2009 pandemic Influenza A (pH1N1) virus infection. However, a comparison of risk factors and outcome during the 2010-2011 post-pandemic period has not been described.


A prospective, observational, multi-center study was carried out to evaluate the clinical characteristics and demographics of patients with positive RT-PCR for H1N1 admitted to 148 Spanish intensive care units (ICUs). Data were obtained from the 2009 pandemic and compared to the 2010-2011 post-pandemic period.


Nine hundred and ninety-seven patients with confirmed An/H1N1 infection were included. Six hundred and forty-eight patients affected by 2009 (pH1N1) virus infection and 349 patients affected by the post-pandemic Influenza (H1N1)v infection period were analyzed. Patients during the post-pandemic period were older, had more chronic comorbid conditions and presented with higher severity scores (Acute Physiology And Chronic Health Evaluation II (APACHE II) and Sequential Organ Failure Assessment (SOFA)) on ICU admission. Patients from the post-pandemic Influenza (H1N1)v infection period received empiric antiviral treatment less frequently and with delayed administration. Mortality was significantly higher in the post-pandemic period. Multivariate analysis confirmed that haematological disease, invasive mechanical ventilation and continuous renal replacement therapy were factors independently associated with worse outcome in the two periods. HIV was the only new variable independently associated with higher ICU mortality during the post-pandemic Influenza (H1N1)v infection period.


Patients from the post-pandemic Influenza (H1N1)v infection period had an unexpectedly higher mortality rate and showed a trend towards affecting a more vulnerable population, in keeping with more typical seasonal viral infection.