30/07/08

More is less in HIV, according to new UNAIDS figures

When UNAIDS put out their new figures yesterday (in a stonking 357-page report), they accompanied it with a press release that began: “New HIV infections and HIV-related deaths declining — however AIDS epidemic not over in any part of the world”. If you made it to the second page of the press release, you’d find that 2.7 people were newly infected in 2007, which, UNAIDS says, “declined from 3 million in 2001”. Deaths have also fallen, to 2.0 million. The total number of people living with HIV, has, however, increased to 33.0 million.

Let’s look at the last report UNAIDS issued, in December 2007. Confusingly, it also gave figures for 2007, but they’re not the same as the figures in the new report. The 2007 report revised previous estimates downwards quite a bit because of better data, largely from India. So it’s not fair to compare the numbers with the 2006 report. But we can compare them with the trend data given in 2006. I’ve pulled out the numbers, and here they are:

Yes, new infections have “declined” since their peak of 3.4 million in 1998. But they appear to be up on 2006. That’s probably an artefact of changing assumptions. The people living with HIV at the end of 2007 should be those who were living with HIV at the end of 2006 (33.27) plus those who got infected in 2007 (2.7 million, if you take the new figures), minus the people who died (2.0 million). By my calculations, that makes 33.97 million men and women, sons and lovers, kids and grandparents, accountants and circus performers and sex workers infected with HIV worldwide. So we’re missing nearly a million.

I understand that estimates change as better data become available, of course. I even bothered to read the UNAIDS backgrounder on methodology (pdf). But I’m still having trouble understanding how the arithmetic works on this one. I’m also wondering if it really worth the sweat of publishing estimates so often. Does the world really need a 50 page report in December 2007, and then another 357 pages seven months later, giving different figures for the same year? Is the marginal increase in accuracy worth the confusion and crushing report fatigue that I’ve heard from so many journalists?

If yes, it would be nice to have the differences explained. Perhaps more cogently than this explanation, which is given in the report: “Even though the HIV prevalence stabilized in sub-Saharan Africa, the actual number of people infected continues to grow because of ongoing new infections and increasing access to antiretroviral therapy.” Besides contradicting the headline statement that prevention is working in heavily-affected countries (i.e. Africa), this is arrant nonsense. Prevalence is the percentage of the population infected with HIV at any given time. It is the product of past rates of new infection (i.e. incidence) and death. The relationship between prevalence and “the actual number of people infected” is determined soley by the number of people in the population. If prevalence is stable but the number of people infected is growing, then it means that the population is growing, nothing else.

It’s worrysome too that Zimbabwe is singled out with Rwanda as a up-there-in-lights HIV prevention success story. The Zimbabwean government has been preoccupied with many things lately, but HIV prevention has not been top of the list. Data show that partner numbers have fallen, but anecdote suggests that it’s in large part because of the political an economic turmoil that has beset the country. Watching one’s father being beaten-up by Robert Mugabe’s goons doesn’t exactly put one in the mood for sex. It might make you want to go out and get plastered, and that might put you in the mood for sex, but with inflation at 2.2 million percent, beer drinking is no longer and option for lots of people. UNAIDS has in the past (rightly) suggested that good leadership is a crucial ingredient of successful HIV prevention. By giving the example of Zimbabwe so much prominence, are they now suggesting we should turn our attention to economic meltdown as a way of reducing multiple partnerships and thus HIV? It might work. The only year that we saw a substantial fall in the proportion of men buying sex in Indonesia was in 1998, the year the economy took a swan-dive off a dliff.

This kind of nit-picking is of course churlish. I sympathise with the writers of reports like this, caught as they are between the need to show that things are going well (so you should keep investing in HIV) and that the situation is dire (so you should keep investing in HIV). In truth, the key issue is not whether there are 2.5 or 2.7 million new infections. It is that somewhere between two and three million people are still getting infected every year with a completely preventable disease that we are spending over 10 billion dollars a year on. That’s a scandal that no amount of report-writing has been able to change.

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This post was published on 30/07/08 in Science.

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  1. Comment by Penelope Chester, 30/07/08, 05:29:

    Great post… It was good to point out the irony in congratulating Zimbabwe on its prevention efforts. Too bad that bureaucratic reports can’t end on the same note you ended this post!

  2. Comment by Ron Rivera, 01/08/08, 08:35:

    It’s worrysome too that Zimbabwe is singled out with Rwanda as a up-there-in-lights HIV prevention success story. The Zimbabwean government has been preoccupied with many things lately, but HIV prevention has not been top of the list.

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