title: Comparison of sexual mixing patterns for syphilis in endemic and outbreak settings.
abstract: BACKGROUND
  In a largely rural region of North Carolina during 1998-2002, outbreaks of heterosexually transmitted syphilis occurred, tied to crack cocaine use and exchange of sex for drugs and money. Sexual partnership mixing patterns are an important characteristic of sexual networks that relate to transmission dynamics of sexually transmitted infections (STIs).
  
  
  METHODS
  Using contact tracing data collected by disease intervention specialists, we estimated Newman assortativity coefficients and compared values in counties experiencing syphilis outbreaks to nonoutbreak counties, with respect to race/ethnicity, race/ethnicity and age, and the cases' number of social/sexual contacts, infected contacts, sex partners, and infected sex partners, and syphilis disease stage (primary, secondary, early latent).
  
  
  RESULTS
  Individuals in the outbreak counties had more contacts and mixing by the number of sex partners was disassortative in outbreak counties and assortative nonoutbreak counties. Although mixing by syphilis disease stage was minimally assortative in outbreak counties, it was disassortative in nonoutbreak areas. Partnerships were relatively discordant by age, especially among older white men, who often chose considerably younger female partners.
  
  
  CONCLUSIONS
  Whether assortative mixing exacerbates or attenuates the reach of STIs into different populations depends on the characteristic/attribute and epidemiologic phase. Examination of sexual partnership characteristics and mixing patterns offers insights into the growth of STI outbreaks that complement other research methods.
authors.affiliation: School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599–7030, USA.
authors.forename: Irene A
authors.initials: IA
authors.lastname: Doherty
authors.forename: Adaora A
authors.initials: AA
authors.lastname: Adimora
authors.forename: Stephen Q
authors.initials: SQ
authors.lastname: Muth
authors.forename: Marc L
authors.initials: ML
authors.lastname: Serre
authors.forename: Peter A
authors.initials: PA
authors.lastname: Leone
authors.forename: William C
authors.initials: WC
authors.lastname: Miller
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D004196:Disease Outbreaks; D019353:Endemic Diseases; D005006:Ethnicity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009657:North Carolina / Q000453:epidemiology; D012424:Rural Population; D012725:Sexual Behavior; D012747:Sexual Partners; D012749:Sexually Transmitted Diseases / Q000453:epidemiology* / Q000208:ethnology / Q000382:microbiology / Q000635:transmission; D013587:Syphilis / Q000453:epidemiology* / Q000208:ethnology / Q000382:microbiology / Q000635:transmission; D055815:Young Adult