Background:
High Rates of Chlamydia (CT) and gonorrhea (GC) infections within San Joaquin County (Northern California) have occurred over the last nine years. The distribution of these infections with respect to the number of repeat and dual infections has not been addressed in detail. To establish better screening methodology and to determine locations to focus education and community outreach efforts, GIS mapping of repeat and dual CT and GC infections was undertaken to discern high prevalence areas within the county.



Objective:
To determine the geographic location of repeat and dual CT and GC cases within San Joaquin County, and to consider how this information can further expand prevention efforts in the county.

Method:
The 23,517 cases of CT and GC reported to Public Health Services were analyzed to determine the number of repeat and dual infections. A repeat infection was defined as ≥2 infections that occurred >30 but ≤365 days apart. Statistical analyses were performed using Excel and SPSS. GIS mapping was performed using ArcView 9.1.

Result:
Of these 23,517 cases, 6,788 cases were either dual infections or repeat cases. There were a total of 111 individuals responsible for 597 repeat GC infections. For CT 1268 individuals accounted for 2886 repeat infections. Transient patterns among patients were observed indicating specific areas to be targeted within San Joaquin County.



Conclusion:
Locations within the county that contained a high prevalence of repeat and dual CT and GC cases were found. As a result, targeted prevention activities and surveillance were considered to increase Public Health Services' interventions.

Implications:
GIS mapping of repeat and dual infections is a tool that local government can use to increase the scientific capacity to locate pockets of infections in communities, and thereby increase the likelihood of more cost effective interventions.