title: Staphylococcus aureus colonization and infection among drug users: identification of hidden networks.
abstract: OBJECTIVE
  We combined social-network analysis and molecular epidemiology to investigate Staphylococcus aureus among drug users.
  
  
  METHODS
  From 2003 through 2005, we recruited adult drug users in Brooklyn, New York. Of 501 individuals recruited, 485 participated. Participants were screened for HIV infection and S. aureus carriage, and they answered a questionnaire assessing risk factors for S. aureus. Participants were asked to nominate up to 10 members of their social networks, and they were invited to recruit nominees to participate.
  
  
  RESULTS
  We identified 89 sociocentric risk networks, 1 of which contained 327 (67%) members. One third of participants were either colonized (20%) or infected (19%) with S. aureus. Overall strain similarity was unusually high, suggesting spread within and across networks. In multivariate analysis, 7 health-related and drug-use variables remained independently associated with infection. Moreover, 27% of nominees were not drug users.
  
  
  CONCLUSIONS
  We found a large, linked, hidden network among participants, with no discernible clustering of closely related strains. Our results suggest that once a pathogen is introduced into a sociocentric network of active drug users, an identifiable community S. aureus reservoir is likely created, with significant linkages to the general population.
authors.affiliation: Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Gwizdala
authors.forename: Maureen
authors.initials: M
authors.lastname: Miller
authors.forename: Meera
authors.initials: M
authors.lastname: Bhat
authors.forename: Peter
authors.initials: P
authors.lastname: Vavagiakis
authors.forename: Christopher
authors.initials: C
authors.lastname: Henry
authors.forename: Alan
authors.initials: A
authors.lastname: Neaigus
authors.forename: Qiuhu
authors.initials: Q
authors.lastname: Shi
authors.forename: Franklin D
authors.initials: FD
authors.lastname: Lowy
mesh_terms: D055030:Drug Users / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D009519:New York City / Q000453:epidemiology; D015995:Prevalence; D012307:Risk Factors; D012944:Social Support; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000209:etiology / Q000635:transmission*; D013207:Staphylococcal Skin Infections / Q000453:epidemiology / Q000209:etiology / Q000635:transmission; D015819:Substance Abuse, Intravenous / Q000150:complications / Q000382:microbiology; D019966:Substance-Related Disorders / Q000150:complications / Q000382:microbiology; D011795:Surveys and Questionnaires