Annmarie Byrne was totally unprepared for the catastrophe which befell her and her family five years ago, for all that she is a clever, articulate woman who has held a senior position in a multinational corporation, run her own business and brought up two children. She was enjoying a happy and comfortable life with her husband of four years in South Africa, when suddenly and unexpectedly he became very ill. Within months he was dead, at the age of 58. He had died of Aids and Annmarie, who had never in her life imagined such an eventuality, had found out she was HIV positive.

"I don't think there is even a word to explain what it is like when you find out," she says. "It was devastating. I thought it happened to other people, I thought it happened to gay people, I thought it happened to black African people and I thought it happened to intravenous drug users. I certainly didn't think it happened to me."

She was living in a country where more than 4.2m adults and children are now estimated to be HIV positive but where the stigma attached to HIV was enormous and where the government was in denial - insisting that poverty rather than the virus was the cause of Aids. She had no idea how to deal with this terrible new knowledge and there was no one to turn to.

"We found out in the April [about my husband] and he died in August. He walked into hospital and came out in a wheelchair and just gave up and died. He didn't want to live any more when he found out. At that time the only drug available was AZT and it was as good as useless."

She did not ask her husband, who had been married before and, she presumed, had had a life between his marriages, how he became HIV positive. "At the end of the day it didn't matter how he got it."

When he died, she did not tell people he had had Aids. "I told everybody my husband had died of cancer because I hadn't told my children, and I'd lost my husband - being diagnosed to losing him was only a short time and I was having to come to terms with that and my own diagnosis. I couldn't deal with telling anybody at that time. But I confided in somebody who actually told other people so I realised that I would have to tell my children quickly before somebody else told them."

That was tough. She had to explain the tragedy over the phone to her 22-year-old daughter who was overseas. More distressing still was the talk with her 14-year-old son and the impact the news had on him. "He stopped smiling. If your mother tells you your deeply loved stepfather has died of Aids, you would probably stop smiling for a long time. It was terrible. It was terrible as well because of the social issues. He couldn't tell anybody. Teenagers have such problems just being teenagers."

They left South Africa for the UK. "Like most people when they are diagnosed, I thought that I was going to die soon. I'd heard about the new drugs on the market and thought if I could get access to those I could see my kids grow up," she says.

Four years on, she is well and not on medication thanks, she says, to Body and Soul, the British support organisation that dedicates itself to helping heterosexual people who are HIV positive and their families. She knows now that the toxic anti-retroviral drugs should not be used until there is no alternative, and both she and her son have learned how to cope with her terminal diagnosis among people who understand and will not treat them as pariahs.

But in the UK, just as in South Africa, those people are the understanding few. The comfortable premises of Body and Soul at London's Royal Homeopathic Hospital are a refuge for many families who may be shunned by their neighbours and whose children never get invited to friends' parties. Some have graffiti daubed on their walls; others have been forced to move house. "The vast majority of people in this country and globally know that racism is bad and judging people by their sexuality is bad but they still think it is OK to judge people who have HIV," says Annmarie. "Having my photo in the Guardian is terrifying me. The fact that that is the case shows that nothing has happened."

She wanted to speak out about her HIV status long ago. She was deeply moved by the speech given to the Durban HIV/Aids conference last year by Nkosi Johnson, the little boy who did more to break the silence around the disease than almost anyone else - and is now dead. But fear of what it might do to her family made her wait until they were old enough and strong enough to deal with the repercussions. Eventually she spoke out to an audience that included Tony and Cherie Blair at a recent theatre benefit to raise money for Body and Soul.

"The love and support that surrounds other illnesses isn't there for people with HIV," she says. "We've spoken for four years about me talking about it because none of us feel any of us has done anything wrong, but just getting to the point where we all felt that I actually could speak out was really terrible. Why should that be, because if I was speaking up for, for instance, breast cancer awareness we'd be surrounded by all the love and support in the world. Why should it be any different for HIV? After all, it's just an illness."

In many ways it is worse than other illnesses. "You do not know which way the illness is going to go. With cancer you know and your doctor knows which form you are going to get. With HIV and Aids you have no idea. So that's terrifying in itself."

Nobody knows how many anxious HIV positive women there are in the country who do not have a clue how long they will stay well and whether they may be facing premature death, but do not dare talk about it with anyone. The numbers of women newly infected with HIV in the UK are now rising much faster than men - more than doubling from 583 in 1996 to 1,240 last year (new male cases rose from 2,097 to 2,311). Paula Harrowing, who co-founded Body and Soul in 1996, thinks the scale of the heterosexual epidemic is not understood and questions the official figures for Aids-related deaths.

"They say there have been 49 deaths in the first two quarters of the year, but that's rubbish. We have had at least 20 here," she says. Death certificates give an end cause, such as pneumonia, but may not mention the HIV virus which so damages the immune system that any other chance infection can become a killer.

But the conspiracy of silence has made people in the UK complacent and doomed those with HIV to ostracism, says Paula - who believes that our attitude to sex is at the root of it. "Everything in life is sold on sex. It impacts on us daily. If you suddenly say that this product can lead to a terminal disease, it doesn't sell. People do not want to think that every time they have a sexual encounter they are at risk."

So they write off HIV/Aids as something that happens to the sort of people they don't want to know. "We have people who come in here and the best thing we can do is hug them because if it is known in their communities, nobody will touch them," says Annmarie.

"Twenty years into the epidemic why is this ignorance still here? Why hasn't it been addressed? Why is there not more publicity and information? Why are schools not being targeted in the right way?"

The group argues that if HIV/Aids is discussed at all in schools, it is presented as a minority hazard - a risk for gay men and drug users. "Women whose lives have been wrecked by it say the messages children are being given are confused. I have to try to teach my children that sex is very special, with the right person at the right time," says Annmarie. "But the world is teaching them that HIV is nasty because it is sexually transmitted and yet we we are all having sex. "

· Body and Soul can be contacted at The Royal Homeopathic Hospital, 60 Great Ormond Street, London WC1 3HR