As a result, d'Agostini, in common with growing numbers of scientists and doctors around the world, is beginning to question whether HIV really is the killer it has been made out to be. He, like them, suspects that many "AIDS" cases are really old diseases given a new name and that people who test HIV-positive are not, as most have been led to believe, the victims of a new, inevitably lethal disease.

As founder of the Nyumbani hospice for abandoned and orphaned HIV-positive children in Nairobi, Kenya, he had expected to see much disease and death. But his so-called "AIDS babies" are confounding all predictions.

A year has passed since the home opened and only one of his first 45 children has been lost an ailing six-week-old infant who had to return to hospital almost immediately and died two weeks later. The rest, who are aged up to six years, are thriving and Nyumbani, which means "at home", teems with life and laughter.

Yet elsewhere in Kenya and across sub-Saharan Africa, according to the World Health Organisation (WHO), tens of thousands of children are dying because of HIV, usually in their first year. Its regional office in Brazzaville says infant mortality has increased so much because of AIDS that gains made in child-survival programmes of recent years are being eroded. WHO says the virus has infected 8m Africans and will be killing 500,000 a year by the end of the century.

But if HIV is causing such havoc elsewhere, why is it apparently proving so innocent in the children of Nyumbani?

D'Agostino, 67, is a former surgeon who trained as a Jesuit priest and became a professor of psychiatry in Washington before going to Africa 10 years ago. "I'm a physician and I bought the theory that HIV is the cause of AIDS," he said. Now he is surrounded by smiling faces that cast huge doubts over it.

"It is surprising. We expected more deaths, and a lot more serious illness. According to most predictions, the children should have died within two to three months of coming to us. Instead, we have now had to set up a nursery school and I'm planning to negotiate their entry into primary school.

"I had also been preparing to establish group therapy for the mothers to deal with their grief at the loss of the children. Instead, the only losses the hospice has are happy ones: some of the children become HIV-negative, and are taken back by relatives or ordinary children's homes."

Even those who persistently test positive are staying well. "I don't have any explanation for it," d'Agostino said. "Will they be alive this time next year? I have no reason to doubt it; they are healthy."

What d'Agostini's hospice provides is very basic care. "They are very sick when they come to us. But as a result of their care here they put on weight, recover from their infections and thrive. Hygiene is excellent. Nutrition is very good. They are really flourishing."

All this is in contrast to the way most children diagnosed as HIV-positive are treated. "People think a positive test means no hope, so the children are relegated to the back wards of hospitals," d'Agostino said. Abandoned by their HIV-positive mothers, the children are killed by multiple infections, malnutrition and misery rather than by AIDS.

At Nyumbani, most of the hands-on work with the children is done by women, usually single mothers, who are quick to bond with the babies in their care. "They have no money and no husband, but they have been mothers that is their big advantage."

Most important to the babies' survival, according to Sister Mary Owens, d'Agostino's assistant, is a big dose of "TLC" tender loving care. "Their whole experience in the home is one that makes them happy children."

Some of the babies become HIV-negative after a few months. The usual explanation for this is that they were never truly virus-infected, but instead inherited their mother's antibodies to HIV, which fade with time. But mothers, too, are being misdiagnosed.

D'Agostino tells of one woman who turned up with her sick baby, begging to be allowed to work for the hospice in return for care for the child. "She had been to hospital seeking treatment for the baby, and they found among other things that it was HIV-positive as well. The baby's grandmother threw both of them out of her house.

"We took them in, and three to four months later sent the baby for another test. It was negative. The mother was delighted. The grandmother took them back. The mother kept working for us and some months later, when she was assigned to go with another child who was to be tested, she asked if she could have a test at the same time and lo and behold, she was negative too."

The experience at Nyumbani flies in the face of the coventional theories about the history of AIDS in Africa. Dr Robert Gallo announced in 1984 that HIV, a newly discovered virus, had been identified as the cause of the immune system breakdown devastating homosexual communities in the United States and Europe. Western doctors invaded Africa with HIV testing kits and computers to map the extent to which people were infected there.

Virus-hunters did succeed in finding large numbers of positive test results, and as far back as 1986 there were said to be 5m HIV-infected people on the continent. Lurid predictions followed, such as one newspaper claim that within 10 years AIDS would leave "vast areas of now-populated land devoid of a single living person".

The tests that led to those estimates are now admitted to have been unreliable, producing a high proportion of false positive results. Newer tests are said to be more accurate, but according to a recent review in the journal Bio/Technology, none has yet been scientifically validated.

The article showed that multiple, non-specific assaults on the immune system, which are extremely common in Africa as a result of poverty, prostitution and the breakdown of medical and social services, may be causing millions to test positive when they are not infected with HIV.

Encouraged by WHO-funded units and numerous non-governmental organisations involved in the fight against AIDS in Africa, doctors are reporting growing numbers of AIDS cases. But researchers have not established the extent to which these are genuinely the result of a new virus, as opposed to a consequence of an intensification in long-established threats to health.

Observers say poverty has driven millions of women into prostitution. Young African males have also been drawn into the trade. "AIDS" deaths are common among these prostitutes, especially when treatment of the resulting repeated infections is either absent or inadequate. Those whose immune systems collapse, as well as those who harbour a cocktail of infections, can become lethally infective.

However, a huge gap remains between this widely acknowledged increase in threats to health associated with prostitutes and their contacts, and the apocalyptic vision of Africa's future espoused by WHO on the basis of its HIV statistics.

As well as using a test that may be useless, these statistics are based on small and often inadequate population samples. Dr Hedvig Pelle, WHO co-ordinator for the Kenya National AIDS Control Programme, said: "AIDS is there. No doubt about it. And it is widespread and increasing. My colleagues in the other countries can tell you the same." But she added: "If you come with this postulate that there are a lot of false HIV-positives, it is very difficult to tell."

Political factors appear to play a part in determining whether a country has a major AIDS problem or not. Kenya lost an estimated Pounds 200m in desperately needed foreign currency in November 1991, when the industrialised world decided to try to force political and economic reform on the country by cutting aid. A recent crisis announcement on AIDS by the country's health minister is seen within the international aid community as an attempt to win back donor sympathy and funds, according to the journal Africa Confidential.

The announcement followed a warning by WHO-sponsored researchers that Kenya alone has an estimated 1m HIV-positive cases, and a cumulative total of 120,000 AIDS victims since the first case was diagnosed in 1985. "A far-from-veiled theory in circulation says figures which show AIDS spiralling out of control have been massaged to extract sympathy," the journal said.

If the HIV theory of AIDS turns out to be flawed, scientists may prove to have done Africans, more than any other people, a huge injustice. Propaganda on the spread of AIDS has discouraged investment, increased poverty and cast a new shadow of fear into the hearts of a people long besieged by health and social problems. *