Countries in Asia and the Pacific can help curb the HIV/Aids epidemic by tackling the spread of the disease in injecting drugs users but must act speedily, UN officials said.

The UN Office on Drugs and Crime's South Asia representative, Gary Lewis, said the virus was still contained in some nations within high risk groups like injecting drug users, but countries had to seize the "window of opportunity".

"That's why it's important to act now, while there is still a degree of containment in high risk groups," Lewis told AFP.

"If we can work to target infections with these communities, we have a real opportunity to contain the spread of the HIV virus into the general population," he said.

Lewis was speaking after a two-day UN-coordinated regional task force meeting in Kuala Lumpur on HIV/Aids amongst injecting drug users (IDUs).

The task force, which includes UN agencies, government representatives and civil society groups, is acting as an advisory group on tackling the spread of the disease amongst that population.

UN officials say the HIV/Aids epidemic is still concentrated among IDUs in some countries such as Malaysia and Vietnam in Southeast Asia, and Nepal and Bangladesh in South Asia.

Various services

The UN estimates that there are between 1.3 and 5.3 million injecting drug users in South and Southeast Asia.

The task force coordinator, Guillaume Le Hegarat, said the group was promoting the "scaling up" of public health services, currently reaching less than five percent of injecting drug users in most countries.

Services include education and needle exchange programs, and treatment options including substitution - using drugs such as methadone to replace illicit drugs, he said.

"Unless we are able to reach at least 50 to 80 percent of the drug user population with these comprehensive services we will have saved lives, but we will not have made a difference in containing and reversing the HIV epidemic," he told AFP .

Le Hegarat said countries had to reach a "critical mass" of injecting drug users to break the transmission of the virus.

"We need to achieve a critical mass in order to make a difference. And not only do we need to reach this critical mass, but we need to do that very quickly, within the next three to five years," he said.

"The epidemic is not waiting for us," he added.