title: Identification of risk factors for infection in an outbreak of Mycoplasma pneumoniae respiratory tract disease.
abstract: BACKGROUND
  Mycoplasma pneumoniae is one of the most common pathogens that causes community-acquired respiratory tract infection. Outbreaks are well known, and all age groups are susceptible. An outbreak in an army training unit afforded an opportunity to identify possible risk factors for morbidity.
  
  
  METHODS
  An outbreak of respiratory illness that occurred in a unit comprising 91 trainees was investigated and analyzed as a cohort study. M. pneumoniae infection was suspected on clinical grounds and was confirmed by polymerase chain reaction, culture, and serologic testing. Data regarding medical history, symptoms, signs, and laboratory tests were collected.
  
  
  RESULTS
  During a period of 12 days, 41 soldiers (45.1%) had respiratory illnesses, of which 10 (11.0%) were pneumonia. Comparison of symptomatic and asymptomatic individuals revealed that smoking was associated with higher rates of disease (risk ratio, 2.1; 95% confidence interval [CI], 1.3-3.2; P<.005) and seroconversion (risk ratio, 2; 95% CI, 1.2-3.4; P=.03). In multivariate analysis, both lower acute immunoglobulin G values (adjusted odds ratio, 7.8; 95% CI, 1.4-42.5; P=.018) and smoking (adjusted odds ratio, 5.6; 95% CI, 1.5-20.4; P=.01) were associated with symptomatic infection; stratification according to smoking status revealed that immunoglobulin G levels among nonsmokers were protective. Patients who had pneumonia had lower lymphocyte counts (1400+/-258 vs. 2000+/-465 cells/microL; P=.001).
  
  
  CONCLUSIONS
  Smoking and lower preexisting immunoglobulin G levels were strongly associated with M. pneumoniae respiratory infection. These findings emphasize the importance of immunity and cessation of smoking for the prevention of disease. The high attack rate emphasizes the extent of infection transmission among healthy persons living in close contact.
authors.affiliation: Army Health Branch, Israel Defense Force, Be'er Sheva, Israel.
authors.forename: Eyal
authors.initials: E
authors.lastname: Klement
authors.forename: Deborah F
authors.initials: DF
authors.lastname: Talkington
authors.forename: Oshri
authors.initials: O
authors.lastname: Wasserzug
authors.forename: Raid
authors.initials: R
authors.lastname: Kayouf
authors.forename: Nadav
authors.initials: N
authors.lastname: Davidovitch
authors.forename: Roger
authors.initials: R
authors.lastname: Dumke
authors.forename: Yael
authors.initials: Y
authors.lastname: Bar-Zeev
authors.forename: Merav
authors.initials: M
authors.lastname: Ron
authors.forename: Jonathan
authors.initials: J
authors.lastname: Boxman
authors.forename: W
authors.initials: W
authors.lastname: Lanier Thacker
authors.forename: Dana
authors.initials: D
authors.lastname: Wolf
authors.forename: Tsilia
authors.initials: T
authors.lastname: Lazarovich
authors.forename: Yonat
authors.initials: Y
authors.lastname: Shemer-Avni
authors.forename: Daniel
authors.initials: D
authors.lastname: Glikman
authors.forename: Enno
authors.initials: E
authors.lastname: Jacobs
authors.forename: Itamar
authors.initials: I
authors.lastname: Grotto
authors.forename: Colin
authors.initials: C
authors.lastname: Block
authors.forename: Ran
authors.initials: R
authors.lastname: Nir-Paz
mesh_terms: D015331:Cohort Studies; D003141:Communicable Diseases / Q000453:epidemiology / Q000382:microbiology; D017714:Community-Acquired Infections; D004196:Disease Outbreaks; D006801:Humans; D008889:Military Personnel; D009177:Mycoplasma pneumoniae; D011019:Pneumonia, Mycoplasma / Q000453:epidemiology* / Q000382:microbiology; D012141:Respiratory Tract Infections / Q000453:epidemiology* / Q000382:microbiology; D012307:Risk Factors