Increasing morbidity of Chlamydia and Gonorrhea cases in San Joaquin County, California : locating high risk areas through GIS analysis of cases from 1997-2006

Morbidity data for chlamydia {CT) and gonorrhea (GC) reported to San Joaquin County (SJC) Department of Health Services (DHS) from 1997 to 2006 was analyzed to geographically locate high risk areas and populations. The largest city in SJC is Stockton, which had the highest incidence rates and highest rates of repeat infections per population, and therefore is the primary focus of this analysis. Rates were determined by dividing the number of infections per census tract by the census 2000 population of each tract. Maps were made first for incidence (cumulative and annual), then for repeat infections, and then coinfections. Census tracts that continually showed high rates of infections were then mapped at the block level to locate more focused areas of infection. Demographic characteristics such as age, gender, race/ethnicity, incarceration, and poverty provided information on the high risk population. Case information was also examined by provider location and the treatment administered. By examining the population characteristics with the highest risk, along with the geographic location, outreach efforts by SJC DHS were far more focused and productive at targeting the core transmissions groups. Also through understanding where the cases were seeking treatment, or identifying a lack of medical availability in certain areas, SJC DHS can contact providers to distribute updated treatment guidelines and educational information to pass on to their patients