UNAIDS “Cures” 6.3 Million With HIV
November 20th, 2007
This is something that happens all too often. Say you’re a medical professional trying to understand the spread of a particularly sexually transmitted disease. What better place to go to study it than the local STD clinic? Just run a survey of the people who show up, and if you’re lucky and the findings are interesting — either they confirm something that others have suspected or they show something new and different from what was believed to be true before — you get to write up a research report, publish it in one of literally hundreds of professional journals, and your small contribution adds to the enormous body of knowledge which continues to accumulate about that disease.
If you’re unlucky however, someone else — say, an anti-gay activist — will read your report and they will write another report which says that everyone behaves just like your sample from the local STD clinic. They do this even though your sample is in no way representative of the general population, or even necessarily representative of STD clinics in other cities. But that’s how we get such nonsense as the so-called “Dutch Study.” Anti-gay activists claim that it “proves” that gay relationships last only 18 months on average and that gay men have some eight additional partners each year while in that relationship. Of course, this is not what that “Dutch Study” demonstrated at all. But no matter. They have their shocking statistic which they use quite often.
So what does it say about the state of our knowledge of the worldwide AIDS epidemic when we discover that epidemiologists — those who are tasked with studying the transmission and control of epidemic diseases — do the same thing as these anti-gay activists?
This morning’s New York Times reported that the UN agency UNAIDS issued a report acknowledging that it had been overestimating the size of the worldwide AIDS epidemic (PDF: 144KB/3 pages) by more than 6 million people, and that the epidemic actually peaked in the late 1990′s. And how did this happen? According to the New York Times:
Until recently, most national estimates were made by giving anonymous blood tests to some young women who came into public health clinics because they were pregnant or feared they had a sexually transmitted disease; those results were expanded with statistical models.
But epidemiologists have realized that such a method — usually applied in big urban clinics because it was more efficient — oversampled prostitutes, drug abusers and people with multiple partners, and ignored rural women. Then the statistical extrapolations exaggerated those errors.
Recognizing this elementary flaw — one they should have recognized from the beginning — UNAIDS now estimates that there are currently 33.2 million people infected with HIV, down from its estimate of 39.5 million from a year ago. It’s as if 16% of the world’s HIV-positive population was cured overnight.
Of course, we know that there was no miraculous cure. It’s just faulty math. And unfortunately, epidemiologists — the very people who should know better — are too often prone to making exactly this kind of error.
Some suggest that there may be political motivations involved in inflating the numbers. After all, jurisdictions which can show that they have a severe problem with a given disease can more easily qualify for grants, discounts, loans and other aid to fund research, prevention and treatment programs. If that’s the case, then this implies that one jurisdiction’s exaggeration may draw badly needed funds from other jurisdictions which act professionally and play by the rules.
It’s hard to tell if that’s a major problem with the UNAIDS surveillance program. Several African countries are now implementing more rigorous surveillance programs, while India has switched to a more representative household survey. UNAIDS says that these two developments are largely responsible for their estimate’s dramatic decrease. But there’s no question that HIV/AIDS is heavily politicized the world over.
I’m glad there are now 6 million fewer people with HIV in the world. It should still concern all of us that there are still maybe 33.2 million, more or less, with HIV. That’s the bigger picture we need to focus on.
But at the risk of drawing too much attention away from that more important picture, I’d like to suggest that there’s another lesson to be learned here. People and statistics are two entirely different things. And sometimes, when you really look at where statistics come from, you may discover that they have surprisingly little to do with the people they purportedly represent. Just try to ask those 6.3 million who were “cured.”