By Craig Timberg
Washington Post Foreign Service
Tuesday, November 20, 2007
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.
Having millions fewer people with a lethal contagious disease is good news. Some researchers, however, contend that persistent overestimates in the widely quoted U.N. reports have long skewed funding decisions and obscured potential lessons about how to slow the spread of HIV. Critics have also said that U.N. officials overstated the extent of the epidemic to help gather political and financial support for combating AIDS.
"There was a tendency toward alarmism, and that fit perhaps a certain fundraising agenda," said Helen Epstein, author of "The Invisible Cure: Africa, the West, and the Fight Against AIDS." "I hope these new numbers will help refocus the response in a more pragmatic way."
Annemarie Hou, spokeswoman for the U.N. AIDS agency, speaking from Geneva, declined to comment on the grounds that the report had not been released publicly. In documents obtained by The Washington Post, U.N. officials say the revisions stemmed mainly from better measurements rather than fundamental shifts in the epidemic. They also say they are continually seeking to improve their tracking of AIDS with the latest available tools.
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.
The United Nations' AIDS agency, known as UNAIDS and led by Belgian scientist Peter Piot since its founding in 1995, has been a major advocate for increasing spending to combat the epidemic. Over the past decade, global spending on AIDS has grown by a factor of 30, reaching as much as $10 billion a year.
But in its role in tracking the spread of the epidemic and recommending strategies to combat it, UNAIDS has drawn criticism in recent years from Epstein and others who have accused it of being politicized and not scientifically rigorous.
For years, UNAIDS reports have portrayed an epidemic that threatened to burst beyond its epicenter in southern Africa to generate widespread illness and death in other countries. In China alone, one report warned, there would be 10 million infections -- up from 1 million in 2002 -- by the end of the decade.
Piot often wrote personal prefaces to those reports warning of the dangers of inaction, saying in 2006 that "the pandemic and its toll are outstripping the worst predictions."
But by then, several years' worth of newer, more accurate studies already offered substantial evidence that the agency's tools for measuring and predicting the course of the epidemic were flawed.
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.
The revisions affect not just current numbers but past ones as well. A UNAIDS report from December 2002, for example, put the total number of HIV cases at 42 million. The real number at that time was 30 million, the new report says.
The downward revisions also affect estimated numbers of orphans, AIDS deaths and patients in need of costly antiretroviral drugs -- all major factors in setting funding levels for the world's response to the epidemic.
James Chin, a former World Health Organization AIDS expert who has long been critical of UNAIDS, said that even these revisions may not go far enough. He estimated the number of cases worldwide at 25 million.
"If they're coming out with 33 million, they're getting closer. It's a little high, but it's not outrageous anymore," Chin, author of "The AIDS Pandemic: The Collision of Epidemiology With Political Correctness," said from Berkeley, Calif.
The picture of the AIDS epidemic portrayed by the newer studies, and set to be endorsed by U.N. scientists, shows a massive concentration of infections in the southern third of Africa, with nations such as Swaziland and Botswana reporting as many as one in four adults infected with HIV.
Rates are lower in East Africa and much lower in West Africa. Researchers say that the prevalence of circumcision, which slows the spread of HIV, and regional variations in sexual behavior are the biggest factors determining the severity of the AIDS epidemic in different countries and even within countries.
Beyond Africa, AIDS is more likely to be concentrated among high-risk groups, such as users of injectable drugs, sex workers and gay men. More precise measurements of infection rates should allow for better targeting of prevention measures, researchers say.