Number of HIV cases overestimated.

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."