Applications of Geospatial Analysis to Surveillance Data: a Spatial Look at Hiv/aids Prevalence in Zambia by Imelda

Human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS) (HIV I AIDS) is a major public health problem in Zambia. Despite some evidence that the pandemic may have reached a plateau or perhaps has begun to decline at the national level, HIV continues to increase in different sub-populations such as adults above 19 years old. The characterization of the spatial patterns of HIV prevalence in the country as well as description of possible determinants of HIV rate variation can direct surveillance efforts and assist in the development of HIV I AIDS control and prevention programs. The spatial distribution of HIV prevalence per district (N=72) in Zambia for periods 1994, 1998, 2002 and 2004 were defined. Using a geographical information system (GIS), a georeferenced database was created. Included in the database were sentinel data, number of pregnant women sampled, age, socio-economic and demographic data, political boundary shapefiles, road network and HIV rates per year. Spatial analysis such as inverse distance weighted (IDW), spatial statistics (Moran's I) and UNAIDS' estimation and projection package techniques were performed. Smoothed maps obtained from both IDW and zonal statistics for the four years under study reveal a spatial variation in HIV prevalence with urban and provincial districts having higher prevalence than rural areas. However, there was an overall trend of decrease in HIV prevalence across the country with the year 2004 exhibiting the most reduction, coinciding with protective sexual behavior campaigns operating in the country. Analysis of regression residuals indicated high spatial autoconelation: Moran's I value was 0.28 (z = 4.12 and p < 0.000) and a highly significant Robust LM (lag), (p < 0.00000), suggestive of a diffusion process.