Winstone Zulu, a member of Thabo Mbeki's Presidential Aids Advisory Panel, was a leading Aids dissident who believed that his HIV-positive status did not mean he would become sick and die.

He refused to take anti-retrovirals until he got a fungal infection so bad that his toenails fell off.

Now the drugs he once thought were toxic have restored his health and he has switched sides in the debate, becoming a powerful voice against the dissident cause.

"I really wanted them to be right," he says sadly. "I think for someone living with HIV like myself, their arguments are even more compelling."

Aids dissidents are a small but vocal group of scientists and activists who believe that HIV does not exist, or that HIV exists it is a harmless virus which does not cause Aids.

They argue that Aids is nothing more than a new name for a string of ailments, like tuberculosis and diarrhoea, that affect people whose immunity has been weakened by poverty and malnutrition. Anti-retrovirals, they claim, are toxic and could kill people who take them.

Zulu, 38, who was the first person in Zambia to go public about being HIV-positive, first came across the dissidents at the 12th International Aids Conference in Geneva in 1998. By then he had been living with the virus for eight years and was an internationally known Aids activist who had played a prominent role in the Paris Aids conference of 1994.

Then he was the chief rapporteur for part of the Geneva event, where a handful of dissidents were on hunger strike. Zulu was intrigued by their arguments, but remained unconvinced. But, he was curious enough to start surfing the Internet for dissident websites when he returned home.

But he continued working for orthodox Aids organisations where he was earning about R7 000 a month - a substantial salary in Zambian terms. He also didn't stop taking the anti-retroviral treatment he had started in 1997.

"Then I got an invitation to sit on President Mbeki's panel," recalls Zulu, who was to become the only non-scientist on South Africa's Presidential Aids Advisory Panel. That invitation, which arrived after three years of questioning, was a turning point in his life.

"With Mbeki coming in, I believed it was the link I needed to believe this," he explains. "When I saw that Mbeki was doubting, I thought this was right."

Mbeki's dealings with dissidents, which began towards the end of 1999, finally convinced Zulu that the dissidents were correct. In February 2000, as the dissident controversy started raging in South Africa, he stopped taking anti-retrovirals.

"What I went through was some kind of denial," Zulu says. "It was such a waste of time. The last two years were such a waste of time. I know some of the people I was with, they just died in denial."

In August last year, Aids dissident Huw Christie, one of the observers at the panel discussions who sat near Zulu during the sessions, died. He had been diagnosed HIV-positive in 1993.

Shortly after Christie's death, Zulu caught a fungal infection which did not respond to treatment. The infection grew steadily worse and eventually all the toenails on his right foot fell off. Even now the nail on his big toe has still not grown back completely.

By the time he started taking anti-retrovirals again in March this year, Zulu was confined to a wheelchair and was too weak to walk. But it was more than his own illness which convinced him that the dissidents were wrong.

Three of his brothers and a sister died after being diagnosed HIV-positive. The youngest was 31 and the eldest 43.

"If it was something that was in the air, the deaths would have cut across age," he said. "Ten-year-olds are not dying at the same rate as people between 20 and 40. This started to make me think - why is the population that's not sexually active still alive?"

These days Winstone Zulu is slowly rebuilding his life.

As he started regaining his health, he wrote to Mbeki to explain why he had changed his mind. The president replied in an email which said: "It is profoundly incorrect and mortally dangerous for many to communicate the message that the only matter of medical concern to us as Africans is HIV."

"Mbeki really was my hero. He's still my hero," Zulu says.

"I think on the Aids point he's got it wrong, but I think on other things, the African Renaissance and so on, he's very progressive.

"I wish he was right, but there's no doubt, I think. I'm talking from personal experience."