Michael Bursaw
Michelle Ginsberg
Over the last seven years, the numbers of new AIDS cases each year in San Diego County has decreased, but not uniformly in each ethnic group or area of San Diego. In this presentation GIS was used to examine trends of AIDS cases over time so that areas of consistently high rates as well as the differences in rates among ethnic groups and transmission modes could be seen in the six health service regions of San Diego. GIS may be a useful tool in allocating AIDS / HIV resources and preventative programs.
The AIDS (Acquired Immunodeficiency Syndrome) epidemic started in San Diego County in 1981 with the first 2 cases being diagnosed. As of March 31, 2001, there have been 10,717 cases of AIDS diagnosed locally, from all age groups, race/ethnic groups, and both genders. From 1981 to 1993, the number of cases increased rapidly each year and since then, the number of new cases per year has been decreasing. The individuals diagnosed with AIDS in San Diego come from many different subpopulations in the County and have varying prevention and treatment needs. As well, AIDS cases are not distributed evenly throughout the San Diego Area. The limited dollars for concentrated treatment and prevention efforts are best utilized in areas most at need and tailored to the population in the local area.
The use of GIS is new to the HIV/AIDS Unit of San Diego County’s Community Epidemiology Program. This is proving to be a useful tool to monitor the changes in the AIDS-community’s demographics so that specific prevention and treatment services can be offered in the areas that have the most need.
San Diego County, occupying 4,261 square miles, is broken down in to 6 distinct Health Service Area regions (HSA), which house a population of more than 2.8 million. Each of these regions varies greatly in size and population density as well as having different demographic characteristics. Since HSA regions are rather large, generalizations about the population based each region has the potential for masking demographic or behavioral characteristics of subgroups contained within. By breaking the regions down into zip codes, more accurate pictures of the various sub-groups within the community demographics can be seen.
Data is collected on those HIV (Human Immunodeficiency Virus) positive people residing in San Diego County at the time they meet the criteria for an AIDS (Acquired Immunodeficiency Disease) diagnosis. Some of the information collected includes the zip code of residence at the time of diagnosis, date of diagnosis, race, gender, age, and mode of transmission. Data is analyzed using SPSS (Statistical Software for the Social Sciences) and imported into ArcView as tables to be joined with the zip codes and region layers.
The County of San Diego funds HIV testing centers and a number of prevention sites geared toward specific communities. The addresses for both HIV testing sites and the sites for prevention programs targeting persons of color, and injection drug users (IDU) were obtained through the San Diego County’s Office of AIDS Coordination and the non-profit organization, Being Alive, and were put into a table. These addresses were then geocoded in ArcView and placed on maps of San Diego County that displayed their target population’s place of residence.
There have been AIDS 10,717 cases diagnosed in San Diego County as of March 31, 2001. While they are distributed throughout the county, the largest concentration of cases is in the Central and North Central HSA Regions. There has, however, been a shift over the time, with an increasing percentage of cases being diagnosed from the South Region and a decreasing percentage of cases from the North Central Region.
Most AIDS cases continue to be seen in men. Scattered throughout the county, however, are female cases with the highest concentration of female cases per zip code in the North Coastal and East regions.
Sex with men continues to be the most frequent risk factor attributed to the acquisition of HIV and subsequent diagnosis of AIDS. Men who engage in sexual relations with other men (MSM) is the predominate risk factor for AIDS in San Diego for more than 90% of the male cases. Heterosexual contact is the risk factor for more than 50% of the female cases
AIDS has been diagnosed in persons of all ethnic backgrounds. In 1993 the number of new cases per year began to decrease in all ethnic groups. It has not, however, decreased uniformly. The percent of new cases attributed to persons of color continue to rise. This rise can be seen in all the regions of San Diego, most noticeably the South region where cases of Hispanic origin make up more than 50% of all cases diagnosed in the area.
ArcView can be a useful tool in planning where to situate HIV testing sites and prevention programs geared toward a specific population. The three regions in the county with the smallest number of AIDS cases have the smallest number of test sites. Central region, which has many more AIDS cases than any of the other regions, has 9 HIV testing sites. When the percent of cases that are attributed to persons of color by zip code of residence is mapped with the prevention programs directed toward persons of color, one can see that there are more HIV prevention programs where this population lives. This is also true when the zip code of residence for those whose exposure to HIV was through injection drug use. When HIV prevention program sites that are specific to IDUs are mapped with the zip code of residence of those who acquired HIV through IDU, the areas with the highest concentration of cases also have the largest number of prevention program sites.
Displaying maps of San Diego County broken down by HSA region and zip code is a useful planning tool. Any information on the population’s demographics or historical mode of HIV transmission can be used to strategically plan targeted HIV prevention efforts. Mapping the location of prospective and current HIV prevention programs in relation to the population it is intended to serve can indicate if sites are too far away from their target population or if too many similarly-targeted programs are placed in close proximity. In addition, plotting AIDS cases by these regions and zip codes can be used for budget planning to meet the varying resource and allocation needs of the different regions. When looking to set up new HIV treatment or prevention programs that meet the unique needs of the targeted client populations it may be more useful to break down the HSA regions into zip codes. HSA regions are so large that they may mask pockets of high AIDS density and behavioral characteristics of sub-groups that can be captured by mapping at the zip code level.
Layers of San Diego County were provided by SANGIS.
Population data was provided by SANDAG.
Tabatha Aboumrad, MPH
Epidemiologist
County of San Diego
Michael Bursaw, MPH
Senior Epidemiologist
County of San Diego
Michelle Ginsberg, MD
Chief, Division of Community Epidemiology
County of San Diego