South Africa has the world's highest incidence of HIV/Aids
Anti-retroviral treatments (ARVs) and universal testing could stop the spread of Aids in South Africa within five years, a top scientist says.
Dr Brian Williams says the cost of giving the drugs to almost six million HIV-positive patients in the country would be $2-3bn per year.
Only about 30% get the life-saving drugs, he said, but early detection and treatment would prevent transmission.
This, he said, should be complementary to the search for an Aids vaccine.
An effective vaccine, he said, was still a long way away.
Dr Williams, a leading figure in the field of HIV research, is based at the South African Centre for Epidemiological Modelling and Analysis (Sacema) in Stellenbosch.
Speaking at at the annual meeting of the American Association for the Advancement of Science (AAAS) in San Diego, he said 30 million people around the world were infected with HIV - with two million dying each year.
"The tragedy is that the disease continues unabated. The only real success story is the development of these extremely effective drugs that keep people alive and reduce their viral load by up to 2,000 times. They become close to non-infectious.
"While the rapid scale-up in the provision of ART in the last five years has exceeded expectations, it has not reduced HIV-transmission and Aids-related TB because it has been given too late in the course of infection."
Dr Williams argued that by the time people started ART, they had infected "most of those that they would have infected anyway".
"We've been using drugs to save lives, but not stop the infection," he said.
"It's time to look beyond that."
He said that if clinical trials started now, all of the HIV positive people in South Africa could be on ARV treatment within five years.
Dr Williams said a few clinical trials were already beginning in the US, Canada and sub-Saharan Africa - and he hoped to have the answer "in one or two years".
Kenneth Mayer, professor of medicine at Brown University in the US state of Rhode Island, agreed that treating patients early with ARVs was a matter of "public health".
The US National Institute of Allergy and Infectious Diseases is planning a trial in New York and Washington - in districts that have an HIV positive population at a similar level to African epidemics.
"We need to get answers [from these trials] quickly. That will help us move forward," Dr Williams said.
"We could break the back of the epidemic. If we can do it, I'm confident it will work."
But Lisa Power, head of policy at the UK HIV charity the Terrence Higgins Trust, said: "We need to be clear; these proposals would very much slow the spread of HIV in areas with generalised epidemics such as sub-Saharan Africa, but they will not stop it by themselves.
"Alongside testing and treatment, education on safer sex and access to condoms remain crucial if we are to contain the epidemic."