The global HIV epidemic could see a resurgence in just five years without a drastic acceleration in efforts to prevent and treat the AIDS virus, the United Nations and disease experts have warned.

While good progress has been made in improving access to life-saving AIDS drugs, an analysis by UNAIDS and an expert panel commissioned by The Lancet medical journal found the rate of new HIV infections was not falling fast enough.

"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 Peter Piot, director of the London School of Hygiene and Tropical Medicine and a lead author of the report.

He said this, plus high demographic growth in some affected countries, was increasing the number of people infected with the incurable virus who would need lifelong treatment.

"Expanding access to treatment is essential, but we will not treat ourselves out of the AIDS epidemic," he said, adding HIV prevention was just as important.

The report said even just sustaining current HIV treatment and prevention efforts would require at least a third of total government health spending in the most affected African countries from 2014 to 2030.

"We have to act now," UNAIDS executive director Michel Sidibe said.

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

Some 35 million people currently have HIV, and since it began spreading 30 years ago, AIDS has already killed 40 million people worldwide.

Recent detailed studies have found clear evidence of resurgent HIV epidemics among high risk populations, such as gay men, in Europe, North America and Asia.

Mr Piot's team also noted that in Uganda, for example, trends in new HIV infections had begun rising again after a decade of success — partly due to HIV prevention getting less attention.

Ben Neuman, a virologist at Britain's Reading University, said the report, while encouraging, also acts as a warning.

"Unless we find new ways to tackle HIV, this creeping killer disease will follow humanity into the 22nd century," he said.

Reuters