title: Seasonality of pathogens causing community-acquired pneumonia.
abstract: Seasonal distribution of microbial aetiology in patients with community-acquired pneumonia (CAP) may add important information both for epidemiologists and clinicians. We investigate the seasonal distribution of microbial aetiology in CAP.
  
  
  
  This prospective observational study was carried out in the Hospital Clinic of Barcelona, Spain (January 2003-December 2014).
  
  
  
  We studied 4431 patients with CAP, of whom 2689 (61%) were males. Microbial aetiology was identified in 1756 patients (40%). CAP was most frequent in winter (34%) but two-third of patients with CAP presented in other seasons. Seasonal variations included Streptococcus pneumoniae (winter 21% vs spring 17% vs summer 14% vs autumn 13%, overall P < 0.001). Influenza viruses were most prevalent in autumn (6%) and winter (5%) compared with spring (3%) and summer (1%) (overall P < 0.001). Legionella pneumophila was most frequent in autumn (4%) and summer (4%) compared with spring (2%) and winter (1%) (overall P < 0.001). Incidence of polymicrobial pneumonia also differed between seasons (winter 7% vs spring 5% vs summer 3% vs autumn 6%, overall P = 0.001). We observed a significant correlation between the lowest seasonal average temperature and polymicrobial pneumonia, pneumococcal pneumonia, and influenza viruses; conversely, L. pneumophila was more common when temperatures were higher.
  
  
  
  CAP should not be regarded as a seasonal disease but occurs throughout all seasons. However, S. pneumoniae, influenza viruses, polymicrobial pneumonia and L. pneumophila are clearly subject to seasonal variations.
authors.affiliation: Department of Pneumology, Hospital Clinic of Barcelona, University of Barcelona (UB), Barcelona, Spain.|Biomedical Research Institute "August Pi Sunyer" (IDIBAPS), Biomedical Research Networking Centres on Respiratory Diseases (CIBERES), Barcelona, Spain.
authors.forename: Catia
authors.initials: C
authors.lastname: Cilloniz
authors.affiliation: Department of Respiratory Medicine and Infectious Diseases, Evangelic Hospital in Herne and Augusta Hospital in Bochum, Bochum, Germany.
authors.forename: Santiago
authors.initials: S
authors.lastname: Ewig
authors.affiliation: Department of Pneumology, Hospital Clinic of Barcelona, University of Barcelona (UB), Barcelona, Spain.|Biomedical Research Institute "August Pi Sunyer" (IDIBAPS), Biomedical Research Networking Centres on Respiratory Diseases (CIBERES), Barcelona, Spain.
authors.forename: Albert
authors.initials: A
authors.lastname: Gabarrus
authors.affiliation: Department of Pneumology, Hospital Clinic of Barcelona, University of Barcelona (UB), Barcelona, Spain.|Biomedical Research Institute "August Pi Sunyer" (IDIBAPS), Biomedical Research Networking Centres on Respiratory Diseases (CIBERES), Barcelona, Spain.
authors.forename: Miquel
authors.initials: M
authors.lastname: Ferrer
authors.affiliation: Department of Microbiology, Hospital Clinic of Barcelona, Barcelona, Spain.
authors.forename: Jorge
authors.initials: J
authors.lastname: Puig de la Bella Casa
authors.affiliation: Department of Infectious Diseases, Hospital Clinic of Barcelona, Barcelona, Spain.
authors.forename: Josep
authors.initials: J
authors.lastname: Mensa
authors.affiliation: Department of Pneumology, Hospital Clinic of Barcelona, University of Barcelona (UB), Barcelona, Spain.|Biomedical Research Institute "August Pi Sunyer" (IDIBAPS), Biomedical Research Networking Centres on Respiratory Diseases (CIBERES), Barcelona, Spain.
authors.forename: Antoni
authors.initials: A
authors.lastname: Torres
mesh_terms: D000328:Adult; D000368:Aged; D017714:Community-Acquired Infections / Q000453:epidemiology / Q000382:microbiology*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012621:Seasons; D013030:Spain / Q000453:epidemiology
keywords: community-acquired pneumonia; microbial aetiology; season; seasonality