THE MOST far-reaching inquiry into the spread of HIV in Britain - to be published next month - shows that about 7,000 men and women have caught the virus through sexual intercourse with the opposite sex.
Scientists have identified several instances where one heterosexual has passed the virus to a second within the United Kingdom, who has then transmitted it to a third British heterosexual.
Furthermore, the team of investigators will say that most of the infected heterosexuals caught the virus from people who have not injected drugs.
The findings undermine the views of the promoters of the heterosexual Aids 'myth', who have argued that the disease is confined to high-risk groups, such as drug users and homosexuals, and that 'normal' heterosexuals need not worry about the risks of being infected with HIV.
Scientists and doctors who helped to compile the statistics on the spread of HIV in Britain said that the figures for heterosexual infections are, in fact, likely to underestimate the true scale of the problem.
Some people, they believe, have contracted the virus through heterosexual intercourse but because they use drugs are nevertheless classified, rightly or wrongly, as having become infected through sharing contaminated needles or syringes.
The report, by a scientific committee chaired by Professor Nick Day, head of the Biostatistics Unit at the Institute of Public Health in Cambridge, will also say that most infected heterosexuals, perhaps as many as 80 per cent, have no idea that they are carriers of HIV. Epidemiologists - who study the spread of diseases - believe that, far from being an insignificant problem, heterosexual Aids in Britain has the hallmarks of being at the earliest stages of a substantial epidemic, although this may take many years to gather momentum.
One of the committee members, Professor Roy Anderson, head of biology at Imperial College in London, said that, in the absence of effective vaccines and drugs to fight Aids, HIV is likely to become an endemic viral infection in a significant minority - perhaps 1 in 10 - of British heterosexuals: 'We're at the early stages of a long-drawn-out epidemic where we don't yet know the endemic level.'
Figures for heterosexual transmission of HIV in the United Kingdom show a consistent and gradual increase in actual reports of infected people - the true figures are much larger as most infected heterosexuals do not come forward for HIV tests because they do not realise that they have put themselves at risk.
Figures for new reports of Aids cases, which are a measure of how HIV was spreading a decade ago, show that the numbers of heterosexually acquired Aids cases in March had displaced Aids acquired through intravenous drug use. This continues a trend that has become increasingly marked over the past couple of years.
Anonymous testing of blood samples, from newborn babies, pregnant women, patients in hospitals and clinics for sexually transmitted diseases, indicate that HIV is continuing to spread slowly within heterosexuals, sowing the seeds for an epidemic over a timespan of decades.
Figures from Scotland, where many heterosexuals became infected initially from sharing contaminated needles, show that heterosexual transmission of HIV is now as frequent as transmission through homosexual intercourse and intravenous drug use.
However, health officials said future predictions of the extent of the heterosexual spread of HIV in Scotland cannot be made with any accuracy as 'a rise in heterosexual transmissions may be taking place now'.
HIV already infects 2 in every 1,000 London women aged between 20 and 34, most of whom - some 1,500 or more in the capital - have contracted the virus heterosexually. Again, scientists believe that this could be an underestimate as a survey of two London STD (sexually transmitted disease) clinics indicates that as many as 7 in every 1,000 female patients had contracted HIV sexually. Professor Day said that as the pool of 7,000 HIV-positive heterosexuals gets bigger, the chances of the virus spreading even faster increases with infected individuals mixing within the population at large. 'The more there is, the more difficult it will be to control,' he said.
Professor Richard Peto, a leading epidemiologist at Oxford University, said that observations of the spread of HIV in other countries are the clearest warning yet that Britain faces a 'monstrous' heterosexual epidemic.
'It shows we are dealing with a virus that can spread in the heterosexual population,' he said. 'It is going to be magic if this virus doesn't spill out into heterosexuals and what works against magic?'
Leading article, page 21