title: Increased incidence of co-infection in critically ill patients with influenza.
abstract: BACKGROUND
  Co-infection is frequently seen in critically ill patients with influenza, although the exact rate is unknown. We determined the rate of co-infection, the risk factors and the outcomes associated with co-infection in critically ill patients with influenza over a 7-year period in 148 Spanish intensive care units (ICUs).
  
  
  METHODS
  This was a prospective, observational, multicentre study. Influenza was diagnosed using the polymerase chain reaction. Co-infection had to be confirmed using standard bacteriological tests. The primary endpoint of this analysis was the presence of community-acquired co-infection, with secondary endpoints including ICU, 28-day and hospital mortality.
  
  
  RESULTS
  Of 2901 ICU patients diagnosed with influenza, 482 (16.6 %) had a co-infection. The proportion of cases of co-infection increased from 11.4 % (110/968) in 2009 to 23.4 % (80/342) in 2015 (P < 0.001). Compared with patients without co-infection, patients with co-infection were older [adjusted odds ratio (aOR) 1.1, 95 % confidence interval 1.1-1.2; P < 0.001] and were more frequently immunosuppressed due to existing HIV infection (aOR 2.6 [1.5-4.5]; P < 0.001) or preceding medication (aOR 1.4 [1.1-1.9]; P = 0.03). Co-infection was an independent risk factor for ICU mortality (aOR 1.4 [1.1-1.8]; P < 0.02), 28-day mortality (aOR 1.3 [1.1-1.7]; P = 0.04) and hospital mortality (aOR 1.9 [1.5-2.5]; P < 0.001).
  
  
  CONCLUSIONS
  Co-infection in critically ill patients with influenza has increased in recent years. In this Spanish cohort, age and immunosuppression were risk factors for co-infection, and co-infection was an independent risk factor for ICU, 28-day and hospital mortality.
authors.affiliation: Multidisciplinary Intensive Care Research Organization (MICRO), Wellcome Trust-HRB Clinical Research, Department of Clinical Medicine, Trinity Centre for Health Sciences, St James's University Hospital, Dublin, Ireland. drmartinloeches@gmail.com.|CIBERes, Madrid, Spain. drmartinloeches@gmail.com.
authors.forename: Ignacio
authors.identifier: http://orcid.org/0000-0002-5834-4063
authors.initials: I
authors.lastname: Martin-Loeches
authors.affiliation: Department of Intensive Care, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Marcus
authors.initials: M
authors.lastname: J Schultz
authors.affiliation: Department of Intensive Care, Erasme Hospital, Université libre de Bruxelles, Brussels, Belgium.
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Vincent
authors.affiliation: Service of Intensive Care Medicine, Parc de Salut Mar, Universitat Autonoma de Barcelona, Barcelona, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Alvarez-Lerma
authors.affiliation: Department of Intensive Care, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Lieuwe D
authors.initials: LD
authors.lastname: Bos
authors.affiliation: Intensive Care Unit, Hospital Universitario Dr. Negrín, CIBERES, Las Palmas de Gran Canaria, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Solé-Violán
authors.affiliation: Hospital Clinic Barcelona, Universidad Barcelona, CIBERES, Barcelona, Spain.
authors.forename: Antoni
authors.initials: A
authors.lastname: Torres
authors.affiliation: Centro de Investigación Biomédica En Red de Enfermedades Respiratorias (CIBERES), Madrid, Spain.|Critical Care Department, Institut d'Investigació Sanitària Pere Virgili (IISPV), Joan XXIII University Hospital, Universitat Rovira i Virgili, Tarragona, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Rodriguez
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D060085:Coinfection / Q000453:epidemiology*; D017714:Community-Acquired Infections / Q000453:epidemiology*; D016638:Critical Illness / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D007251:Influenza, Human / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D013030:Spain / Q000453:epidemiology
keywords: Co-infection; Influenza; Intensive care; Outcome; Risk factors