Geographic identification of high gonorrhea transmission areas in Baltimore, Maryland.

Geographic approaches to sexually transmitted infection (STI) research frequently seek to identify areas where outreach STI testing may most effectively interrupt continued transmission of STIs. Many of the studies are limited, however, in that they fail to control for racial/ethnic composition of the high prevalence areas. These studies thus may be merely identifying the broader sexual networks of the high morbidity population and not the high transmission networks within them. Cluster detection analysis may be an appropriate approach to identify critical STI disease transmission locations. This study determined whether statistically significant geographic clusters of high prevalence gonorrhea cases can be located after controlling for race/ethnicity. Using a spatial scan statistic, the authors analyzed reported cases of gonorrhea (n = 32,454) in Baltimore City, Maryland, from 1994 to 1999 geocoded to the primary address and aggregated to census block groups (n = 709). They adjusted for the underlying distribution of the population aged 15-39 years and percent African American per census block group. The results identified eight significant clusters of high STI prevalence areas, reinforcing the inference that risks for gonorrhea are associated with definable sociogeographic spaces. The areas identified may be critical to control STIs and may provide important direction for further study and targeted interventions.