While the world is at last making progress against the disease, thanks to a massive increase in spending, better access to drugs and growing awareness, huge problems remain, the UN agency coordinating the fight against HIV/AIDS warned.
In its report, issued on the eve of a UN General Assembly session on the disease, UNAIDS underlined the dangers caused by prevention programmes which it said in many countries were still far off-target and inaccessible to millions of people.
"Overall, the HIV incidence rate (the proportion of people who have become infected with HIV) is believed to have peaked in the late 1990s and to have stabilised subsequently, notwithstanding increasing incidence in several countries", UNAIDS said in the latest Report on the Global AIDS Epidemic.
However, the agency warned that there was no room for complacency. "We know what needs to be done to stop AIDS. What we need now is the will to get it done", the report said.
AIDS has killed more than 25 million people since it was first recognised in 1981, UNAIDS said, while the HIV virus which precedes the disease infected 65 million people over the same period.
Last year AIDS claimed the lives of 2.8 million people and over 4.1 million were newly infected with HIV, according to the report. In 2003, the UN estimated that 4.8 million were newly infected with HIV.
An estimated 38.6 million people were living with HIV at the end of 2005, the vast majority of whom were unaware that they were infected, it added.
Warning from UN chief
UN Secretary General, Kofi Annan has warned that there is still much to be done in the fight against HIV/AIDS.
"We need to continue be vigilant and to redouble our efforts, particularly with young people and of course also press for the protection of women, today AIDS has a woman's face, more than 50 percent of those being infected are women and young people and this is where we really need to be vigilant and work hard and I hope that the discussion this week will re-energise the international community and communities dealing with epidemic, to go back to the grass roots and continue the fight," said UN Secretary General, Kofi Annan, at the launch of the report.
The UNAIDS report is based on detailed country-by-country estimates that the Geneva-based agency carries out only once every two years.
It pointed to "important progress" over the past five years, in the wake of a landmark 2001 UN summit which laid down targets for halting and starting to reverse the AIDS epidemic by 2015.
However, there is still "extraordinary diversity" in the epidemic, with a mixture of success and failure, it said. The disease is also predominantly spread by heterosexual sex.
Millions of victims
Sub-Saharan Africa remains by far the worst-affected region, being home to two-thirds of all people living with HIV.
Two million people died of AIDS in the region last year and there were 2.7 million new infections.
While the epidemic in South Africa - one of the worst in the world - showed no evidence of a decline, other African countries nonetheless made major progress.
HIV prevalence fell in Kenya and Zimbabwe, as well as in urban areas of Burkina Faso.
"In the rest of sub-Saharan African, the majority of epidemics appear to be levelling off", said UNAIDS.
Elsewhere, there were declines in Cambodia and Thailand, but prevalence rose on China, Indonesia and Vietnam.
India overtook South Africa as the world's worst-affected country in terms of the absolute number of people with HIV, although not as a proportion of the population. Epidemics in the former Soviet Union also spiralled.
Global resources for the fight against AIDS last year reached 8.3 billion dollars - well within the range fixed by the UN summit in 2001. But annual needs are set to reach 22 billion dollars by 2008, UNAIDS said.
Access to antiretroviral drugs in developing nations has improved, it said. About 1.3 million were receiving them in 2005 - up from 240,000 people in 2001, although the figure was still less than half the goal of three million set by the UN.
In a grimmer assessment, UNAIDS said that less than one in five people in the world who risked HIV infection had access to basic prevention such as condoms and other safe sex measures, or programmes specifically aimed at helping drug users or prostitutes.
In addition, only one in eight people worldwide who want to be tested for HIV are currently able to be so.
Scaling up prevention and treatment could avert 29 million new infections by 2020, UNAIDS said.