title: Space-time migration patterns and risk of HIV acquisition in rural South Africa.
abstract: To quantify the space-time dimensions of human mobility in relationship to the risk of HIV acquisition.
  
  
  
  We used data from the population cohort located in a high HIV prevalence, rural population in KwaZulu-Natal, South Africa (2000-2014). We geolocated 8006 migration events (representing 1 028 782 km traveled) for 17 743 individuals (≥15 years of age) who were HIV negative at baseline and followed up these individuals for HIV acquisition (70 395 person-years). Based on the complete geolocated residential history of every individual in this cohort, we constructed two detailed time-varying migration indices. We then used interval-censored Cox proportional hazards models to quantify the relationship between the migration indices and the risk of HIV acquisition.
  
  
  
  In total, 17.4% of participants migrated at least once outside the rural study community during the period of observation (median migration distance = 107.1 km, interquartile range 18.9-387.5). The two migration indices were highly predictive of hazard of HIV acquisition (P < 0.01) in both men and women. Holding other factors equal, the risk of acquiring HIV infection increased by 50% for migration distances of 40 km (men) and 109 km (women). HIV acquisition risk also increased by 50% when participants spent 44% (men) and 90% (women) of their respective time outside the rural study community.
  
  
  
  This in-depth analysis of a population cohort in a rural sub-Saharan African population has revealed a clear nonlinear relationship between distance migrated and HIV acquisition. Our findings show that even relatively short-distance migration events confer substantial additional risk of acquisition.
authors.affiliation: aDepartment of Statistics, Department of Biobehavioral Nursing and Health Systems, Center for Statistics and the Social Sciences, and Center for Studies in Demography and Ecology, University of Washington, Seattle, Washington bAfrica Health Research Institute, University of KwaZulu-Natal, Mtubatuba, South Africa; Institute for Public Health, Faculty of Medicine, University of Heidelberg, Heidelberg, Germany; and Department of Global Health and Population, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA cAfrica Health Research Institute, University of KwaZulu-Natal, Mtubatuba, South Africa dAfrica Health Research Institute, School of Nursing and Public Health, University of KwaZulu-Natal, Durban; Centre for the AIDS Programme of Research in South Africa - CAPRISA, University of KwaZulu-Natal, Congella, South Africa.
authors.forename: Adrian
authors.initials: A
authors.lastname: Dobra
authors.forename: Till
authors.initials: T
authors.lastname: Bärnighausen
authors.forename: Alain
authors.initials: A
authors.lastname: Vandormael
authors.forename: Frank
authors.initials: F
authors.lastname: Tanser
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D015658:HIV Infections / Q000453:epidemiology*; D063426:Human Migration; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D018570:Risk Assessment; D012424:Rural Population; D013019:South Africa / Q000453:epidemiology; D062211:Spatio-Temporal Analysis; D055815:Young Adult