Background:
Richmond, Virginia is consistently ranked among the highest cities in the country for gonorrhea and chlamydia rates.

Objective:
The objective of this research was to examine the geographic epidemiology of sexually transmitted diseases (STD) in Richmond, Virginia and to employ an ecological regression study design to assess the correlation between STD rates and census-block-aggregated per capita income levels, drug arrest rates, and percent African-American population.

Method:
The study population included pooled geocodable cases (N= 8159) of gonorrhea and chlamydia diagnosed for three years (2000-2002) in Richmond. First, a geographic analysis, using the spatial scan statistic, identified highly probable (p<.0001) clusters of high STD rates at the block group level. Second, a spatial linear regression technique was applied to the data (Y2000) after diagnostics of the ordinary least squares (OLS) model confirmed significant spatial autocorrelation.

Result:
Before and after adjusting for spatial effects, high incidence rates of STDs were strongly correlated (p<0.0001) with all the independent variables tested.

Conclusion:
Tight clustering indicates core theory operational in Richmond, Virginia. The core is characterized by high degrees of poverty, certain types of crime, and racial uniformity.

Implications:
From a surveillance perspective, this analysis illustrates that the spatial scan statistic can be a useful tool for identifying neighborhoods of core STD transmission in an urban area.