Sir Donald Acheson, the former government Chief Medical Officer, warned the British Association's annual meeting that 'these people by definition have no idea they have been at risk. They tend to be diagnosed when they are already ill and have been infectious for some time'. Half of those studied had never suffered from any other sexually transmitted disease.
Sir Donald warned that 'it seems to me inevitable that HIV from this small heterosexual pool will continue to spread', although the increasing incidence would at first appear imperceptible.
It could take 30 years for the prevalence to grow from one in 100,000 to 1 per cent, he said. But by then more than half a million people would be infected.
There were also signs that fewer homosexual men were practising safe sex. 'The loss of friends and the fear of death has but a temporary effect on behaviour,' he continued. Cases of anal gonorrhoea, risky behaviour, and a spate of new infections have recently reappeared among gay men. Latest figures show that no fewer than one in four homosexual men attending venereal disease clinics in London are infected with HIV, compared to one in 60 heterosexual men.
Globally, the cumulative economic cost of the Aids pandemic by the end of 1991 may be as high as dollars 240bn ( pounds 125bn) - most of it in the lost earnings of sufferers, rather than medical bills.
According to Dr Andrew Cliff, from Cambridge University, Aids has already cost the US some dollars 170bn ( pounds 89bn) in economic losses. But, while Western countries had the resources to bear these costs, the outlook is bleak for the poorer countries of Africa, where the disease is widespread.
By the end of the century the cost of Aids to Uganda could represent the equivalent of the entire contribution of the country's manufacturing industry to its economy. Some of the world's poorest nations would experience an Aids- related recession.
Dr Cliff also provided evidence that contact between soldiers and prostitutes played the most important role in the spread of heterosexual Aids in Uganda. Previous explanantions of the spread of the disease in Africa have highlighted lorry drivers and prostitutes or the effects of urbanisation.
Dr Chris McGuigan, a chemist at Southampton University, claimed that he had developed a compound which may be more effective than AZT in treating HIV infection.
According to Dr McGuigan, the compound, So221, acts in a similar manner to AZT but is less toxic. It appears particularly effective in tackling the virus inside a type of white blood cell where AZT does not work very well and HIV can 'hide out'.
However, pharmaceutical companies appeared less optimistic as the compound has only been tested in the laboratory. 'Many companies have compounds which look superior to AZT in the lab, the real issue is whether they work in people,' Ray Baker, director of chemistry at Merck, Sharp and Dohme, said.
Reported Aids cases in the UK rose to 6,279 in July - up 139 on June. The total number of deaths reached 3,913 last month, up 74 on the June figure.Reuse content