South African surgeons have carried out the world's first organ transplants from one HIV-positive person to another, in a groundbreaking operation that opens the way to saving thousands of lives.

Doctors transplanted HIV-infected kidneys from a single donor into two men in late September at Groote Schuur hospital in Cape Town, where Christiaan Barnard performed the world's first heart transplant. The operations were not made public until it was clear they had been successful.

The South African authorities had previously blocked HIV-positive people from receiving transplants and discarded nearly a third of organs because the potential donors were carrying the virus that causes Aids - a policy criticised by some people in the medical establishment of a country where one in five adults is HIV-positive.

But the ban was lifted last year, opening the way for more operations, and possibly giving HIV-positive patients a greater chance of receiving new kidneys than those not infected with the Aids virus, because there are more potential donors.

The surgeon who performed the operations, Dr Elmi Muller, said the condition of both patients was "excellent", the transplanted kidneys were functioning well and there were no signs of rejection.

"HIV patients are at a disadvantage when it comes to getting an organ and dialysis. Even when we try to be fair, they are at a disadvantage competing with people with no chronic illness," she said. "This study opens up an opportunity to help them, even gives them a slight advantage, because of the high number of HIV-positive donors."

Muller said that if the kidney transplants were successful in the long term it would open the way to the use of other organs such as livers, which are particularly vulnerable to damage by anti-Aids drugs, and hearts.

Nonetheless, the transplants remain controversial because they almost certainly mean that the recipient will become infected with the virus strain that infected the donor, which may be different from the one they carry and increase their resistance to anti-Aids drugs.

There are also concerns that HIV-positive organs could themselves have been damaged by the disease, making them less durable as transplants.

But news of the transplants has brought new hope to many. Dr June Fabian, a consultant nephrologist at Johannesburg hospital, said some of her HIV-positive patients stood to benefit from accepting HIV-positive organs.

"[If you have] renal failure and HIV you get told to go home and die," she said. "HIV-positive to HIV-positive [transplants] come from having limited resources and knowing that the patient is going to die. Positive to positive [transplant] is the last alternative.

"This offers hope for a large population of people who previously had no hope for dialysis and transplantation."

Among those who will potentially benefit is one of Fabian's patients, a 50-year-old businessman who did not wish to be named. A tough and fit man before his kidneys failed, he was diagnosed HIV positive last year.

He now does his own dialysis at home through a implant in his stomach. Four times a day he pours a bag of fluid down a tube into his stomach, and a little while later drains it out again.

It is an improvement on the in-hospital dialysis machines he was using before. That involved being attached to machines for four hours a day, three times a week. "It's better, but hectic. You have to do the thing the whole day, there is little else you can do. Now time is hard, it is hard to live, hard to earn something, to look after my business," he said. "If I can get a [transplant] I will be the happiest man ... I still have belief that one day I'll get a donor."

The transplants present special problems. HIV-positive organ recipients will already be on drugs to boost their immune systems, but a transplant requires treatment to suppress the immune system so the new organ is not rejected.

In theory, the two sets of drugs work at cross purposes but, although doctors cannot fully explain it, international research has shown that HIV-positive people who have received organs free of the virus do as well in the long term as patients who do not have HIV.