KAMPALA, Sept 8 (AFP) - Talking openly about AIDS in Uganda, where the disease has claimed half a million lives, has helped to cut the rate of HIV infection by half over the last six years, according to the professor heading a national programme.

Before the launch of a huge public awareness campaign six years ago, AIDS and HIV were taboo subjects, not discussed in public, and covered up when known to be the cause of a relative's death.

Now the disease is frequently raised by politicians, and talked about in schools, the workplace and in the home.

According to John Rwomushana, Director General of the Uganda Aids Commission (UAC), a campaign to bring HIV/AIDS into the open has paid off, with infection rates in the most affected areas and among the most sexually active age groups showing dramatic falls.

"This trend can be attributed to public awareness campaigns, free family talk and discussions of the problem and a concerted effort to prevent further infections," Rwomushana told AFP.

"Generally, the rate has been reduced by about 50 percent. The infection rate in the most affected areas like Kampala has been reduced from 30 to 12 percent (of the population), while the general prevalence is reduced from 10 to 7 percent," he said.

These days, some 90 percent of Ugandans "know quite well all the ways the disease is transmitted."

The campaign features roadside billboards advising "If you can't abstain, use a condom," as well as seminars and workshops.

Ugandans are encouraged to test for HIV infection. The process is free, quick and accompanied by counselling.

HIV/AIDS nevertheless remains a considerable health problem in Uganda, where at least 1.5 million people, 7.5 percent of the population, are estimated to be HIV-positive.

Rwomushana realises there is much work to be done.

"We are looking at a strategic planning in a more comprehensive manner that has not yet been done before which will include intensified research and more community outreach programmes," he said.

Aids campaigners such as Rwomushana have found adversaries in religious quarters. The Roman Catholic church in particular is opposed to encouraging the use of condoms, claiming this promotes promiscuity.

Ugandans use some 80 million condoms annually. The government plans to import 10 million to meet demand.

Children are among the worst-affected sector of society. A million children are thought to have been orphaned by AIDS and many have become family heads at a very young age.

In some communities only the children and elderly remain.

"They can no longer manage the strenuous peasantry farming. Weeds in some shambas have overgrown because there is nobody to attend to these plantations," social worker Florence Kiwanuka told AFP.

Ninety percent of Uganda's economy derives from small-scale agriculture. "The impact of the disease on the economy is potentially devastating," according to Rwomushana.

Better news has emerged at the laboratory level, with breakthroughs being made in halving the transmission of HIV from expectant mothers to their children. "The implications of this study for developing countries where 95 per cent of the AIDS epidemic is occurring are profound," said Brooks Jackson of Johns Hopkins University School of Medicine, one of several US experts working on the joint project.

The treatment under development costs a fraction of drugs such as AZT, and it is projected to protect some 300,000 new borns every year.

Encouraging results have also been seen in an experimental vaccine, Canary pox Alvac, being simultaneously tested here and in Brazil and Thailand.