How reliable are the figures?

In the welter of grim estimates outlining the depth of Africa’s AIDS crisis, one nagging question remains: How reliable are the figures?

According to UNAIDS, the estimates are provisional and updated as improved knowledge becomes available. “This improved knowledge along with methodological advances together provide the basis for UNAIDS/WHO updates of the HIV/AIDS estimates for countries, regions and the world,” an agency briefing paper noted.

UNAIDS estimates there are 9.9 million AIDS orphans in Africa. That figure, for the number of children born infected or orphaned by HIV-positive women, is based on new evidence that women with HIV ultimately become less fertile - they go on to bear around 20 percent fewer children than they otherwise would - and has actually been adjusted down from earlier projections.

“The basic point is that all the time data collection improves, and as it improves, the knowledge of the disease improves,” Richard Delate, UNAIDS spokesman in South Africa, told IRIN.

AIDS activists, however, acknowledge that there can be problems with statistics “based on assumptions upon assumptions”. The “only assumption we can make is to look at the trends,” a doctor working on AIDS in the South African military told IRIN.

“I think there are massive gaps in information gathered on HIV prevalence (the estimated total number of people infected) and HIV incidence (the actual infection rates). It can actually undermine a lot of advocacy,” Mark Haywood of South Africa’s AIDS Law Project added.

The main method used for assessing HIV/AIDS prevalence is anonymous testing of women at ante-natal clinics. Although it provides accurate raw data, the difficulty is its interpretation. According to Patrice Mashaba of South Africa’s Medical Research Council, one problem is the assumption that “there is a ratio of one partner to each pregnant woman.” Another issue is a regional and class bias. Not all woman have access to ante-natal clinics, while others attend private facilities, he noted.

“Better information becomes available about HIV spread when countries set up more representative ‘sentinel sites’ to monitor infection rates,” UNAIDS argues. For Asia and Latin America, that has witnessed the scaling back of earlier prevalence estimates. But, the agency stresses: “The most important message is that there is no room for complacency about AIDS.”