Doing this would cost more initially but then save money down the road because there would be fewer HIV-infected people to treat, Reuben Granich and colleagues at the World Health Organization wrote in the journal The Lancet.

The researchers emphasized their findings do not represent new WHO policy or any other guidance but rather stand as a call for discussion on how to better tackle the AIDS epidemic and the role of so-called antiretroviral drugs.

"Although other prevention strategies, alone or in combination, could substantially reduce HIV incidence, our model suggests that only universal voluntary HIV testing and immediate initiation of antiretroviral drugs could reduce transmission to the point at which elimination might be feasible by 2020 for a generalized epidemic, such as that in South Africa," they wrote.

Granich and colleagues used data from South Africa as a test case for a generalized epidemic in their model, which assumed all HIV transmission was through heterosexual sex.

This showed that voluntary screening in which at least 90 per cent of the population took part, and immediate drug treatment for those testing positive, could reduce HIV transmission by more than 95 per cent within 10 years.

The AIDS virus infects an estimated 33 million people globally, mostly in sub-Saharan Africa, and has killed 25 million. There is no cure.

The advent in the 1990s of combination drug therapy called highly active antiretroviral therapy, or HAART, has extended the lives of many HIV-infected people, particularly in developed countries.

About 3 million people worldwide had received the drug cocktails by the end of 2007, far short of the estimated 6.7 million infected people still in need of treatment, the researchers added.

There are, of course, drawbacks which the researchers and other scientists pointed out. One is how health systems in poor countries can cope with widespread testing, and whether people can stick to the drugs they must take for life.

"At its best, the strategy would prevent morbidity and mortality for the population, both through better treatment of the individual and reduced spread of HIV," Geoffrey Garnett, a researcher at Imperial College London, wrote in a commentary in The Lancet.

"At its worst, the strategy will involve over-testing, over-treatment, side effects, resistance, and potentially reduced autonomy of the individual in their choices of care."