More than 28 million Africans are now living with HIV/AIDS and in some countries over 30 percent of the adult population is infected, a UNAIDS statement warned on Tuesday.
"The devastating impact of HIV/AIDS is rolling back decades of development progress in Africa," said Peter Piot, UNAIDS executive director.
"Every element of African society - from teachers to soldiers to farmers - is under attack by AIDS," he added.
In data released on the eve of the Group of Eight (G-8) summit on Wednesday, which is due to consider the New Partnership for Africa's Development (NEPAD), UNAIDS estimated that the rate of economic growth in sub-Saharan Africa had fallen by up to four percent because of the pandemic.
Meanwhile, according to a new UN study, prevention campaigns have successfully raised awareness of HIV/AIDS in developing countries, but have not had a major impact on behaviour. People still refuse to accept that they are at risk of catching the HI virus.
A United Nations Population Division study of 24 countries in Africa, seven in Asia and eight in Latin America and the Caribbean found that even in places where there is a high prevalence of HIV/AIDS, most people feel the risk of contracting AIDS is low.
In some countries - Ghana, Kenya, Malawi, Uganda, Tanzania and Zimbabwe - virtually the entire adult population was aware of HIV/AIDS, the study noted.
In most countries, awareness of AIDS was higher among men than women.
"Radio is by far the most often cited source of knowledge about AIDS. About half of the female respondents and more than 7 in 10 male respondents have heard about AIDS on the radio," the report said.
Schools and teachers appear to play little a limited role in AIDS awareness. According to the study, schools and teachers were mentioned by fewer than 10 percent of the respondents.
The report said that among respondents who were aware of HIV/AIDS, a "large majority" knew of at least one way to protect themselves from contracting the disease.
Yet in half the countries surveyed, one-quarter to one-third of female respondents knew of no way to avoid getting HIV/AIDS. In Mozambique, two-thirds of female respondents knew of no way to avoid getting HIV/AIDS.
Using a condom and having one sex partner were the two most popular answers. Many respondents said they were limiting sexual partners to avoid infection.
But fewer than eight percent of women and between 15 percent and 25 percent of men said they had begun using condoms in their sexual relationships, the report noted. The percentage of couples who used condoms was very low in all countries surveyed.
"The results from this study highlight the enormous challenge lying ahead in the prevention of the spread of HIV/AIDS. Clearly, dramatic changes in sexual and reproductive awareness and behaviour in many less developed countries are needed in order to defeat the HIV/AIDS epidemic," the report said.
Released to commemorate the one-year anniversary of the first UN General Assembly Special Session on HIV/AIDS, the report is the largest international study on HIV/AIDS ever completed by the United Nations. The study was based on surveys of about 5,000 households in each country, and was conducted mainly during the mid-to-late 1990s.