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Tuesday, November 20, 2007

AIDS numbers downsized: Learning experience

AIDS numbers are about to be downsized, which should be good news for everyone: According to Craig Timberg of the Washington Post,
JOHANNESBURG, Nov. 19 -- The United Nations' top AIDS scientists plan to acknowledge this week that they have long overestimated both the size and the course of the epidemic, which they now believe has been slowing for nearly a decade, according to U.N. documents prepared for the announcement.

AIDS remains a devastating public health crisis in the most heavily affected areas of sub-Saharan Africa. But the far-reaching revisions amount to at least a partial acknowledgment of criticisms long leveled by outside researchers who disputed the U.N. portrayal of an ever-expanding global epidemic.

The latest estimates, due to be released publicly Tuesday, put the number of annual new HIV infections at 2.5 million, a cut of more than 40 percent from last year's estimate, documents show. The worldwide total of people infected with HIV -- estimated a year ago at nearly 40 million and rising -- now will be reported as 33 million.

Yes, 33 million is 33 million too many, and no, AIDS is not directly related to the purpose of this blog. But one thing this story demonstrates is the hazards of statistics gathering, which is, at times, very much related to the purpose of this blog. For example,

Among the reasons for the overestimate is methodology; U.N. officials traditionally based their national HIV estimates on infection rates among pregnant women receiving prenatal care. As a group, such women were younger, more urban, wealthier and likely to be more sexually active than populations as a whole, according to recent studies.

[ ... ]

Newer studies commissioned by governments and relying on random, census-style sampling techniques found consistently lower infection rates in dozens of countries. For example, the United Nations has cut its estimate of HIV cases in India by more than half because of a study completed this year. This week's report also includes major cuts to U.N. estimates for Nigeria, Mozambique and Zimbabwe.

Well, it makes sense that old people (a growing category in any community that benefits from peace, sanity, clean water, and modern technology) wouldn’t be at quite the same risk for AIDS ...

The main thing to see is that the critics of alarmism were right. There was and is a big problem, but it wasn’t exactly the problem we thought. A clearer picture means focusing on the real problems.

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