Using GIS to spatially portray the prevalence of HIV/AIDS and Tuberculosis...

Using GIS to spatially portray the prevalence of HIV/AIDS and Tuberculosis and its demographic consequences in selected countries in sub-Saharan Africa

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Rajendran  Pillay
Rajendran Pillay
University of the North, P. O. Box 3604, 0700 Pietersburg
Limpopo Province, South Africa
Tel: Int+(0)15-268-2995, Fax: Int+(0)15-268-2892 or 268-2323
Email: [email protected]

Background
With the onset of the new millennium Sub-Saharan Africa is currently the epicenter of HIV/AIDS infection with 23.3m at the beginning of 2000 (Mail & Guardian, 2001) and with the worldwide estimates pegged at 51,32m (Mail & Guardian, 2003). Sub-saharan Africa thus has 70% of world infections in an area that has only 10% of the global population. The HIV/AIDS disease knows no boundaries, but spatial epidemiology through cartographical analysis may yield vital clues as to HIV distribution (clustered or random) across communities with different norms and socio-economic status. Moreover, researchers have placed a closer relationship between TB and HIV/AIDS and argue that the two diseases are known for activating and reactivating each other. With HIV increasing the chance of reactivating dormant TB infection from 10% to 50% during a person’s life per year (DOH, 1997) and recent studies have suggested that 40% of all TB cases are attributed to HIV infection. Cartographic and GIS techniques would also assist in developing measures for monitoring the geographical spread of the HIV/AIDS pandemic over three years and TB and HIV incidence levels over two years in selected countries across sub-Saharan Africa.

Methods
A base map for the HIV/AIDS mapping would be constructed for the purpose of HIV/AIDS spatial portrayal over the three years and TB and HIV incidence levels over two years. Using ArcView GIS, HIV/AIDS prevalence data and HIV and TB incidence levels from three countries are cartographically mapped retrospectively from 1997 to 2000 to show current trends in the spread of the HI virus and HIV versus TB geographic dispersion. Further, choropleth techniques would show the rates of incidence of the HI virus per administrative district level for the selected countries over three years and also look at some consequences to their respective district populations. The accumulative effect of an increase in HIV/AIDS per district over a set period: 1997 to 2000 and HIV versus TB over a two year period would also be spatially portrayed via choropleth mapping.

Results
Whiteside and Sunter (2000) reckons that AIDS claims 5 500m men, women and children everyday in Africa. Studies conducted in both rural and urban areas in nine different African countries showed more women affected than men (13:10); this is continuing to skew the demography of many African countries with men outnumbering women. An interesting turnaround in HIV/AIDS prevalence is only visible in Uganda. In many of the other African countries a mortality decline by 25% between 1997 and 2004 and life expectancy from about 66 to 49years by 2004 is quite possible. South Africa is most frightening with the KwaZulu-Natal Province, South Africa being consistently high at 32.5%. In 1998, the Mpumalanga province in South Africa had the second highest prevalence rate (30%) but dropped to 27.9% in 1999 putting the province in the third place behind the Free State. One of the lowest prevalence occurs in the Limpopo Province (LP), South Africa, where a sample survey in 2000, based on 1808 blood specimens, found 238 (13.2%) women attending ANC’s to be HIV positive. This was a 1.77% increase from 1999’s 11.43% and a 5% increase from the 1997’s 8.2% (DOH, 2000).

According to Pulse Track (1998) the MRC diagnosed 107 000 cases of Tuberculosis in 1997 with 18 964 reported TB cases in the Western Cape Province, South Africa alone, an increase of 26% from its 1997 levels of 15 034, with KZN Province ranked a close second at 9 672 (1998) reported TB cases, a mere 4% reduction from 1997 (10 075 TB cases). Ironically, the Limpopo Province, South Africa recorded the lowest TB cases in 1998 (2 112), a drop of 8% since 1997 (1 947) and this province also ranked among the one of the lowest HIV prevalence rates in South Africa with a drop of 2.77 % to 8.73% in 2000 from 11.5% (1998). According to WHO (2000) 9.4m people were infected with TB and HIV throughout the world and it doubles every year. However, WHO (2000) states that 70% (6.58m) of them live in Sub-Saharan Africa (UNAIDS, 2000). South Africa recorded a 32.8% HIV + TB cases (1998) from an estimated 180 507 TB cases against a TB incidence of 419/100 000 population. Of this the KZN province recorded the highest HIV + TB cases (49.8%) from an estimated 39 650 TB cases against a TB incidence of 433/100 000. The Western Cape was tagged the lowest at 16.8% of 22 942 estimated TB cases against a TB incidence value of 614 per 100 000. The impact on life expectancy, fertility, mortality and dependency ratio versus HIV and TB would also be highlighted using choropleth cartographic mapping techniques for the 1998 – 2000 period.

Kamanga et al’s (2000) study in Zambia showed that HIV has increased the burden of TB in Sub-Saharan Africa. They continue to argue that prevalence rates for TB in Zambia are over 400/100 000 population per year attributed largely due to an increase in HIV infection rate. Being HIV+ constitutes a risk factor for progressing from TB infection to TB disease (DOH, SA 2000). In their analysed HIV-1 seroprevalence study among TB clinic attendants in Africa, Shandera et al (2000) found the mean and median HIV-1 prevalence for TB clinic attendants was 20 and 16.8% respectively for all 28 nations, and 28,2% for attendants in Central, South, and East Africa. Interestingly, this research effort brings out similar comparisons between the selected Sub-Saharan countries and Shandera et al’s studies in Africa.

Conclusion
The spatial dynamics of this pandemic and the association of TB with HIV can be portrayed using Cartographic and GIS techniques via choropleth mapping of HIV/AIDS and TB prevalence data. Moreover, the emerging patterns of the spread of HIV/AIDS and HIV and TB, within the different districts, of the three selected countries over a three year period may provide some guidelines to the possible trend that HIV/AIDS would take over the next four year cycle and how the relationship between HIV and TB would pan out towards the approach of the new millenium and more importantly its demographic impact on key population indicators for example life expectancy. This study, however, argues the need to for appropriate clinical, educational and social programs to secure some control or curtailment on the spatial spread of TB and the HI virus in sub-Saharan Africa by 2004.