By FRANCIS KAJUMO

Recently, there have been claims of success against the Aids pandemic in various African countries. The enduring, and sometimes only statistic given, is an estimate of the national Aids prevalence rate.

This figure is controversial but necessary because the data is generally collected from pre-natal clinics and expectant mothers who need to be tested for HIV antibodies.

The data is taken from any number of clinics, then correlated with figures of known Aids-related deaths from various hospitals, and then extrapolated statistically to fit the larger national populations.

The limitations of this approach are obvious. Not all women visit these clinics, and even if they did, the causes of their deaths are not always accurately documented. Without an HIV test either before or after death, one cannot really determine whether a death is related to Aids.

Arguments can be made about the number of the sentinel points, whether they are in rural or urban settings, or whether they are representative of their national populations.

Be that as it may, prevalence rates are important indicators if they are measured properly. However, there is an inherent fallacy in the drop in prevalence rates because most people assume that a falling rate is a sign of success.

Prevalence is a dynamic statistic and a drop would indicate that the number of new infections does not exceed the number of Aids deaths. A high number of Aids deaths is a negative reflection of the national strategy, meaning that very few people are on life-extending drugs.

For instance, a country like Senegal has had a very low prevalence rate - less than 6 per cent - with a background of very low Aids-related deaths for the past 20 years.

This can be interpreted to mean that certain efforts such as religious, cultural, preventative programmes or abstinence have successfully kept the general population from contracting HIV, and that this low figure is not because of a concomitant high Aids death rate.

Ironically, a static Aids prevalence rate could mean either that there are no new cases and no Aids-related deaths (a success story), or that the number of new Aids cases offsets death from Aids (a dubious success story). 

Thus, when Kenya claims that its Aids rate has dropped from 14 to 10 per cent, the claim begs the question whether this is, in fact, a success story. 

Other questions arise as to whether there were any new infections (within the last year or so) or whether these were people infected 10 or even 20 years ago and just recently got tested.

It is important because this could be a reliable indicator of whether national preventative efforts are working. A national prevention programme can only be considered successful if there are fewer new cases than in preceding years. Unfortunately, there is no reliable way of establishing whether cases are new or old unless the general population routinely underwent voluntary HIV testing.

Our solution is, therefore, to focus only on six annual criteria to establish whether Aids funding is being efficiently utilised. 

The factors are: 1) the number of new voluntary counselling and testing centres (VCTs); 2) the number of people who report to VCTs; 3) the percentage of people who test positive at these centres; 4) the percentage of people who come back for testing and the percentage who bring their sex partners; 5) the percentage of HIV-positive people who are subsequently put on anti-retroviral treatment; 6) the number of Aids-related deaths reported.

The formula for success would include an increase in all but numbers 3 and 6, and such data can all be reliably collected and collated at a national level.

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Mr Kajumo is a science/Aids researcher, Albert Einstein Medical School, New York, and the director of Kenya Aids Watch Institute (KAWI)