THE global HIV epidemic will be pushed into "irreversible decline" in less than a decade if drugs are used to prevent the spread of the virus as well as for treatment, according to the World Health Organisation.

New guidelines unveiled by the health body at the International Aids Society conference in Malaysia today will recommended for the first time using antiretroviral drugs as a way to reduce the risk of transmission of the virus.

Antiretroviral drugs help to prevent HIV transmission because if the virus can be reduced to "undetectable" levels in the blood, the risk of passing it on falls significantly.

Dr Margaret Chan, director-general of WHO, said the recommendations could have an "unprecedented impact" if they were introduced, helping to prevent three million deaths and 3.5 million new infections between now and 2025.

She said this prospect – which was unthinkable just a few years ago – can now "fuel the momentum needed to push the HIV epidemic into irreversible decline".

And nearly 30 years after the "don't die of ignorance" tombstone adverts, the reality of an "Aids-free" generation could occur in the near future, Scottish experts have said.

Philippa Easterbrook, a scientist at WHO in the department of HIV, said there was now compelling evidence that antiretroviral drugs used to treat HIV at an earlier stage could also help prevent infections.

She said a "tipping point" could be reached by 2021 when the numbers who need to start treatment globally will decrease for the first time.

"We are preventing infections all the time, as more and more people start treatment, but at the same time there are more and more people being diagnosed," she said.

"At that point in 2021, we will have finally turned it around so the number of new people being diagnosed does not exceed the number that are being put on therapy. So the number needing to start therapy will decline."

She added: "The importance is of really keeping the momentum going in challenging economic times with other priorities – we are winning, but there is still a long way to go."

New figures from WHO show the increased use of antiretroviral treatment is already having an impact: globally, the number of Aids-related deaths decreased from 2.3 million in 2005 to 1.7 million in 2011. In South Africa, life expectancy rose from 54 to 60 years between 2005-11, largely due to antiretroviral treatment.

One key recommendation among the raft of new guidelines is that HIV treatment is started at an earlier stage, when the immune system is still considered to be "normal". Currently treatment is usually given only at the stage when the immune system has been impacted by the virus, leaving the body more vulnerable to infections.

The guidelines say treatment should now be given when the CD4 cell count – which measures the health of the immune system – is at 500, instead of waiting until it falls to around 350, the current recommendation in the UK.

Robert McKay, national director for Terrence Higgins Trust Scotland, said: "There is no cure for HIV, absolutely – but the advances we have made over the last 10 years in particular have been tremendous."

George Valiotis, chief executive of HIV Scotland, said stigma still surrounding HIV meant there was an issue with getting people diagnosed at an earlier stage. "When we change that, that is when we can start to look at an irreversible decline," he said.

Charity Waverley Care recently launched a campaign funded by the Scottish Government to tackle stigma. It features films capturing the experiences of people living with HIV. Information packs have been sent to secondary schools and will be go out to churches later this year.

Grant Sugden, chief executive of Waverley Care, pointed out that one of the issues the charity was now dealing with was older people who are living with HIV.

Sudgen said: "Now people (with HIV) are over 50, over 60 years old and getting the same conditions that anyone ageing gets – that is a challenge for services.

"At the same time it is something to celebrate, as it means treatment is effective and people are leading healthy lives.

"When someone is diagnosed early now they can have a normal life expectancy – that is a really important message."

He said the WHO guidelines on earlier antiretroviral treatment could bring huge public health benefits.

"I think it is very exciting in terms of looking at having an Aids-free generation at some point, which is very much what they are talking about," he added.

Guidelines from the British HIV Association (BHIVA) – which set standards in the UK – recommend treatment be given when the CD4 count is around 350, but that patients should be able to start treatment at any count if they wish to reduce their risk of transmitting the virus.

Duncan Churchill, chair of the BHIVA treatment guidelines group, said the WHO recommendations would be taken into account during its next major revision of advice, due to be published in spring 2014.

But he added the evidence was not yet fully clear on the benefits of starting treatment earlier.

He said: "The problem we have in the UK is not when you start people on treatment. It is the fact that 24% of people who have HIV infection are unaware of their status and as a consequence are likely to present late. Our priority very much needs to be diagnosing people earlier. "

A spokeswoman for the Scottish Government said that clinicians in Scotland followed guidance issued by the BHIVA. She added: "Our biggest challenge is to diagnose HIV as soon as possible."