title: The epidemiological dynamics of infectious trachoma may facilitate elimination.
abstract: BACKGROUND
  Trachoma programs use mass distributions of oral azithromycin to treat the ocular strains of Chlamydia trachomatis that cause the disease. There is debate whether infection can be eradicated or only controlled. Mass antibiotic administrations clearly reduce the prevalence of chlamydia in endemic communities. However, perfect coverage is unattainable, and the World Health Organization's goal is to control infection to a level where resulting blindness is not a public health concern. Here, we use mathematical models to assess whether more ambitious goals such as local elimination or even global eradication are possible.
  
  
  METHODS
  We fit a class of non-linear, stochastic, susceptible-infectious-susceptible (SIS) models which allow positive or negative feedback, to data from a recent community-randomized trial in Ethiopia, and make predictions using model averaging.
  
  
  RESULTS
  The models predict that reintroduced infection may not repopulate the community, or may do so sufficiently slowly that surveillance might be effective. The preferred model exhibits positive feedback, allowing a form of stochastic hysteresis in which infection returns slowly after mass treatment, if it returns at all. Results for regions of different endemicity suggest that elimination may be more feasible than earlier models had predicted.
  
  
  CONCLUSIONS
  If trachoma can be eradicated with repeated mass antibiotic distributions, it would encourage similar strategies against other bacterial diseases whose only host is humans and for which effective vaccines are not available.
authors.affiliation: F.I. Proctor Foundation, University of California, San Francisco, CA, 94143-0412, USA.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Lietman
authors.forename: Teshome
authors.initials: T
authors.lastname: Gebre
authors.forename: Berhan
authors.initials: B
authors.lastname: Ayele
authors.forename: Kathryn J
authors.initials: KJ
authors.lastname: Ray
authors.forename: M Cyrus
authors.initials: MC
authors.lastname: Maher
authors.forename: Craig W
authors.initials: CW
authors.lastname: See
authors.forename: Paul M
authors.initials: PM
authors.lastname: Emerson
authors.forename: Travis C
authors.initials: TC
authors.lastname: Porco
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D002692:Chlamydia trachomatis / Q000472:pathogenicity*; D005002:Ethiopia / Q000453:epidemiology; D006801:Humans; D008954:Models, Biological; D011157:Population Dynamics; D013269:Stochastic Processes; D016019:Survival Analysis; D014141:Trachoma / Q000188:drug therapy / Q000453:epidemiology* / Q000635:transmission*
chemical_list: D000900:Anti-Bacterial Agents