The most effective way to used AIDS drugs in South Africa would be to concentrate on cities, although this might also be the least ethical approach, an international team of researchers said on Monday.

A computer model suggested the most efficient strategy for the country’s plan to give triple-drug therapy to half a million people by 2008 would be to focus on cities. However that would mean neglecting sick people in the countryside and widening the health divide between urban and rural areas.

The computer model tested three different approaches, using real data from South Africa’s KwaZulu-Natal region including one plan that concentrated on the region’s capital, Durban.

“The Durban-only drug allocation strategy would prevent the greatest number of infections (an additional 15,000 infections by 2008),” the researchers wrote in a report published in the Proceedings of the National Academy of Sciences.

Health facilities are concentrated in big cities, said Sally Blower, a professor at the Semel Institute for Neuroscience and Human Behavior at the University of California Los Angeles, who led the study.

“Some places are remote and fairly difficult to get to,” she said in a telephone interview.

This would worsen already bad health inequalities between Durban and the countryside. “Thus the Durban-only strategy would be the least ethical,” the researchers wrote.

The model found that treating only residents of Durban, and giving no drugs to people elsewhere in the province, would reduce the number of new infections by 46 percent.

Deaths from AIDS would fall by 42 percent in Durban but by only 0.1 percent in rural areas.

If the drugs were shared equally between city and country, transmissions would fall by between 11 percent and 28 percent in Durban and by 17 percent to 37 percent in rural areas. AIDS-related deaths would fall by 26 percent in Durban and 34 percent in rural communities.

South Africa has 5.4 million people infected with the virus - one in nine people.

The government was slow to act against the epidemic, with President Thabo Mbeki at first questioning whether the human immunodeficiency virus caused AIDS, and then questioning the safety of drugs that can control the incurable virus.

More recently, Health Minister Manto Tshabalala-Msimang has promoted alternatives like garlic and lemon juice, prompting scientists and activists to call for her to be sacked.

The government started distributing triple-drug cocktails in 2004 but Blower said it had not yet thought through the epidemiological consequences.

“If you have got rational planning, you can balance ethics and epidemiology and make cool, calm, rational decisions,” she said, adding that the researchers were not telling the South African government what to do.

“We are definitely not saying this is what should happen because we are not policymakers. I know that it could be very upsetting, as it should be, if North Americans are basically seen as telling them what they should be doing in their own country,” she said.