The geography of sexual partnerships in Baltimore: Applications of core theory dynamics using a geographic information system

Objective: Gonorrhea has a focused geographic distribution characterized by high incidence rates in defined "core" areas and decreased incidence as th e radial distance from the central core increases. Dense core group transmi ssion has long been hypothesized. Methods: We have previously mapped sexually transmitted disease (STD) rates in Baltimore census tracts using STD morbidity data interfaced with a geog raphic information system, Core areas were defined using a standard definit ion based on gonorrhea distribution. We studied spatial distance patterns b etween sexual partners, using the residential addresses of 572 individuals, representing 286 dyad partnerships recruited as part of an epidemiology an d behavioral study. To determine if partners lived closer together than wou ld be expected, a modified bootstrap algorithm using Monte Carlo models was developed to compare the distances between partners' residences and all ot her possible residences. Results: Two distinct (east and west) core areas were previously identified . Compared with randomly selected Baltimore addresses, partners tended to r eside closer to one another than would be expected by chance (z = -1.8), wi th a median distance of 1.7 kilometers, Within the core areas, women reside d a median of 547 meters from their partner, and men resided a median of 33 9 meters from their reported partners. When all partnerships were considere d, the median distance was 1,699 meters. Of the 500 simulation models, the minimum median distance was 4,889 meters, Conclusions: Partners of patients in core areas in Baltimore live remarkabl y close to one another, and the partner selection patterns in general indic ate nonrandom distribution, Geographic information system-determined patter ns of STD patients residing in hyperendemic census tracts support the core theory of disease transmission, In these areas, targeted geographically bas ed interventions may be warranted.