The world is not ready for the full social and economic impact of AIDS, which has killed more than 20 million people in the past quarter century, the World Health Organization warned Tuesday.

The U.N. agency said unless nations pulled together to defeat it, AIDS would destroy any hope of a better life for tens of millions, including non-sufferers, living in abject poverty around the globe.

The world at large “is far from ready for what is to come” - catastrophic social and economic consequences for many communities and countries if the epidemic continued unchecked, WHO said in its annual report.

“Although it has seemed a familiar enemy for the last 20 years, HIV/AIDS is only now beginning to be seen for what it is: A unique threat to human society whose impact will be felt for generations to come,” it said.

It was already undermining the U.N. Millennium goals of eradicating by 2015 extreme poverty and hunger, reducing infant and maternal mortality and the spread of other diseases, and achieving universal primary education, it added.

WHO’s annual report on key aspects of international health - this year focusing on AIDS, the leading cause of death among 15-59 year-olds worldwide - is to be presented at the agency’s annual assembly next week.

The 170-page report, entitled “Changing History,” injected a small note of optimism into the overall gloom emerging from its AIDS statistics - 34-46 million people infected, with five million joining them every year.

A concerted international effort to get the latest treatments to sufferers and promote ways to avoid infection could turn the tide, it said, even though no vaccine was in sight despite years of research.

It cited many cases - in the Caribbean, Latin America, Africa and Asia - where the latest antiretroviral drugs had pulled sufferers back from the brink of death and restored them as active citizens contributing to their national economies.

But of the six million people in developing countries who need the therapy, only 400,000 got it last year, the report said. More than 90 percent of victims live in just 34 countries.

The report said although Africa is home to two-thirds of all people living with the disease, it accounts for only 11 percent of the world’s total population of some six billion.

About one in 12 African adults is infected.