title: Prevalence of Atypical Pathogens in Patients With Cough and Community-Acquired Pneumonia: A Meta-Analysis.
abstract: Community-acquired pneumonia (CAP), acute cough, bronchitis, and lower respiratory tract infections (LRTI) are often caused by infections with viruses orStreptococcus pneumoniae. The prevalence of atypical pathogensMycoplasma pneumoniae,Chlamydophila pneumoniae,Legionella pneumophila, andBordetella pertussisamong patients with these illnesses in the ambulatory setting has not been previously summarized. We set out to derive prevalence information from the existing literature.
  
  
  
  We performed a systematic review of MEDLINE for prospective, consecutive-series studies reporting the prevalence ofM pneumoniae, C pneumoniae, L pneumophilaand/orB pertussisin outpatients with cough, acute bronchitis, LRTI, or CAP. Articles were independently reviewed by 2 authors for inclusion and abstraction of data; discrepancies were resolved by consensus discussion. A meta-analysis was performed on each pathogen to calculate the pooled prevalence estimates using a random effects model of raw proportions.
  
  
  
  Fifty studies met our inclusion criteria. While calculated heterogeneity was high, most studies reported prevalence for each pathogen within a fairly narrow range. In patients with CAP, the overall prevalences ofM pneumoniaeandC pneumoniaewere 10.1% (95% CI, 7.1%-13.1%) and 3.5% (95% CI, 2.2%-4.9%), respectively. Consistent with previous reports,M pneumoniaeprevalence peaked in roughly 6-year intervals. Overall prevalence ofL pneumophilawas 2.7% (95% CI, 2.0%-3.4%), but the organism was rare in children, with only 1 case in 1,765. In patients with prolonged cough in primary care, the prevalence ofB pertussiswas 12.4% (95% CI, 4.9%-19.8%), although it was higher in studies that included only children (17.6%; 95% CI, 3.4%-31.8%).
  
  
  
  Atypical bacterial pathogens are relatively common causes of lower respiratory diseases, including cough, bronchitis, and CAP. Where surveillance data were available, we found higher prevalences in studies where all patients are tested for these pathogens. It is likely that these conditions are underreported, underdiagnosed, and undertreated in current clinical practice.
authors.affiliation: Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, Georgia.
authors.forename: Christian
authors.initials: C
authors.lastname: Marchello
authors.affiliation: Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, Georgia.
authors.forename: Ariella Perry
authors.initials: AP
authors.lastname: Dale
authors.affiliation: Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, Georgia.
authors.forename: Thuy Nhu
authors.initials: TN
authors.lastname: Thai
authors.affiliation: Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, Georgia.
authors.forename: Duk Soo
authors.initials: DS
authors.lastname: Han
authors.affiliation: Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, Georgia ebell@uga.edu.
authors.forename: Mark H
authors.initials: MH
authors.lastname: Ebell
mesh_terms: D001886:Bordetella pertussis / Q000302:isolation & purification; D016993:Chlamydophila pneumoniae / Q000302:isolation & purification; D017714:Community-Acquired Infections / Q000453:epidemiology* / Q000382:microbiology; D003371:Cough / Q000453:epidemiology* / Q000382:microbiology; D006801:Humans; D016952:Legionella pneumophila / Q000302:isolation & purification; D009177:Mycoplasma pneumoniae / Q000302:isolation & purification; D018410:Pneumonia, Bacterial / Q000453:epidemiology*; D015995:Prevalence
keywords: Bordetella pertussis; Chlamydophila pneumoniae; Legionella pneumophila; Mycoplasma pneumoniae; community acquired pneumonia; cough; respiratory tract infection