The world risks a deadly AIDS rebound unless countries most affected by the virus expand access to antiretroviral treatments and boost their focus on stopping new infections, said a new UN report issued Thursday.

Sustaining current HIV treatment and prevention efforts in the most affected African countries over the next 15 years would require at least a third of total government health expenditures, according to the findings of the study released by the Joint United Nations Programme on HIV/AIDS (UNAIDS) and famed medical journal, The Lancet.

On top of emphasizing the growing need for continued international support for these countries, the report also revealed a five-year window for preventing AIDS rebound in a bid to roll back the killing disease.

"We have to act now. The next five years provide a fragile window of opportunity to fast-track the response and end the AIDS epidemic by 2030," Michel Sidib, executive director of UNAIDS, said in a press release.

"If we don't, the human and financial consequences will be catastrophic."

The report acknowledged that unprecedented progress has been made over the years toward increasing access to HIV treatment globally.

The United Nations, in fact, has steadily been rolling out a so- called fast-track approach highlighting the need to focus on the counties, cities and communities most affected by HIV, and recommends that resources be concentrated on the areas with the greatest impact in order to end the AIDS epidemic by 2030.

In particular, the approach calls for efforts in the 30 countries that together account for 89 percent of new HIV infections worldwide. To fast-track national responses in these 30 priority countries will require extensive mobilization of human, institutional and strategic international partners, as well as significant commitments from both national and international sources, UNAIDS said.

Despite some advances in the battles against the disease, however, the UNAIDS-Lancet report warns that the rate of new HIV infections is not falling fast enough. This, combined with high demographic growth in some of the most affected countries, is increasing the number of people living with HIV who will need antiretroviral therapy to stay alive.

As a result, the study calls for an urgent need to scale up AIDS efforts, calls on governments to ramp up HIV prevention efforts, and continue expanding access to treatment.

"We must face hard truths -- if the current rate of new HIV infections continues, merely sustaining the major efforts we already have in place will not be enough to stop deaths from AIDS increasing within five years in many countries," said Professor Peter Piot, director of the London School of Hygiene & Tropical Medicine and lead author of the report.

"Expanding sustainable access to treatment is essential, but we will not treat ourselves out of the AIDS epidemic. We must also reinvigorate HIV prevention efforts, particularly among populations at highest risk, while removing legal and societal discrimination," he said.

Meanwhile, the report also highlighted the need to ramp up funding.

Current efforts cost in the order of 19 billion U.S. dollars per year, "whereas it will take 36 billion (U.S. dollars) annually to achieve the UN goal" for 2030, it said.

In poor, badly-hit African countries, the campaign will require as much as 2.1 percent of gross domestic product annually and at least a third of government health expenditure, it said.

"This clearly demonstrates that international support to the AIDS efforts in these countries will be needed for many years to come," the authors said.