© 2017 The Authors Background Influenza A (H1N1)pdm09 virus infection acquired in the hospital and in critically ill patients admitted to the intensive care unit (ICU) has been poorly characterized. Aim To assess the clinical impact of hospital-acquired infection with influenza A (H1N1)pdm09 virus in critically ill patients. Methods Analysis of a prospective database of the Spanish registry (2009–2015) of patients with severe influenza A admitted to the ICU. Infection was defined as hospital-acquired when diagnosis and starting of treatment occurred from the seventh day of hospital stay with no suspicion on hospital admission, and community-acquired when diagnosis was established within the first 48 h of admission. Findings Of 2421 patients with influenza A (H1N1)pdm09 infection, 224 (9.3%) were classified as hospital-acquired and 1103 (45.6%) as community-acquired (remaining cases unclassified). Intra-ICU mortality was higher in the hospital-acquired group (32.9% vs 18.8%, P < 0.001). Independent factors associated with mortality were hospital-acquired influenza A (H1N1)pdm09 infection (odds ratio: 1.63; 95% confidence interval: 1.37–1.99), APACHE II score on ICU admission (1.09; 1.06–1.11), underlying haematological disease (3.19; 1.78–5.73), and need of extrarenal depuration techniques (4.20; 2.61–6.77) and mechanical ventilation (4.34; 2.62–7.21). Conclusion Influenza A (H1N1)pdm09 infection acquired in the hospital is an independent factor for death in critically ill patients admitted to the ICU.
- Community-acquired infections
- Critically ill
- H1N1 subtype
- Infuenza A virus
- Nosocomial infection