This is the VOA Special English Health Report.

United Nations officials now say fewer people than they thought are infected with the virus that causes AIDS.

Last year, the agency known as UNAIDS estimated that thirty-nine and one-half million people were living with H.I.V. On Tuesday it reduced that by sixteen percent to a little more than thirty-three million.

Agency officials say the lower number represents better information and information from more countries. The single biggest reason, however, was an intensive re-examination of India's epidemic. At the same time, the agency reduced its estimates for five African countries: Angola, Kenya, Mozambique, Nigeria and Zimbabwe.

Also, UNAIDS says it now believes the number of new H.I.V. cases per year reached a high in the late nineteen nineties at more than three million. This year, it estimates that two and one-half million people became infected, and that two million people died of AIDS.

Yet even as the number of new infections has dropped, the number of people living with H.I.V. is increasing. Better treatments are extending lives, and more people are getting the drugs.

Also, the new report says prevention efforts appear to be changing risky behavior in several of the countries most affected by H.I.V.

But U.N. officials say AIDS is still one of the leading causes of death worldwide and the major cause in Africa. African death rates remain high, they say, because treatment needs are not being met.

Sub-Saharan Africa had almost seventy percent of the new cases of H.I.V. reported this year. But UNAIDS officials say this is a notable reduction since two thousand one.

Many scientists who study epidemics have long argued that the agency has been overestimating the extent of H.I.V. worldwide. They say national estimates have been based mostly on findings from high-risk groups in large cities.

The lower estimate just released came from more studies of wider society, including rural areas. Even so, experts say there is a need to further improve the research methods.

Billions of dollars are being spent to prevent and treat H.I.V. Activists worry that the new estimate may lead to a drop in financial support. But UNAIDS officials say it does not change the need for immediate action and more money. They warn that in some countries, infection rates were falling but are now rising again.

And that’s the VOA Special English Health Report, written by Caty Weaver. You can learn more about AIDS at voaspecialenglish.com. I'm Steve Ember.