Data from the Public Health Laboratory Service (PHLS) presented to the International Aids conference in Berlin yesterday shows that the number of people infected through heterosexual intercourse now outstrips those infected by injecting drugs.
The unlinked anonymous blood screening survey in England and Wales, which began in 1990, suggests that 27,200 people are now HIV positive (within a range of 20,200 to 34,300). More than half (14,900) are homosexual or bisexual men; drug users account for 4,500 cases, while heterosexual intercourse was a route of transmission for 6,300 cases. An estimated 1,500 people were infected through blood transfusions.
A second study by the PHLS of HIV infection among women in London aged between 20 and 34, during 1991-1992, showed that the number infected through sexual intercouse (300) may equal the number infected by injecting drugs. The incident of HIV was estimated as two per thousand cases in this group.
The data compiled by the PHLS and researchers from St Mary's Medical School, University College Hospital and Middlesex Medical School, and the London School of Hygiene and Tropical Medicines gives the most precise picture to date of the spread of HIV. It will form the basis of a government report by Professor Nicholas Day, head of the biostatistics unit at the Institute of Public Health in Cambridge, to be published later this month.
Dr Karl Overton and colleagues from the Communicable Disease (Scotland) unit at Ruchill Hospital, in Glasgow, presented evidence that the nature of the HIV epidemic in Scotland is changing. In 1985, the number of injecting drug users infected with HIV was 160, and the number of heterosexuals was three. New cases of HIV peaked in drug users in 1986, with a figure of 202, and have fallen to 45 in 1991.
In heterosexuals, the figure for 1991 is 42. For homosexual and bisexual men over the same period, the number of new cases have fallen from 71 to 51. 'Initially associated mainly with injecting drug users in Edinburgh, this component of the (HIV) epidemic has declined markedly, while there has been a relatively small increase in the reports of infections for the heterosexual population of the major population centres,' researchers concluded.
In contrast, a study of people attending a sexually transmitted disease clinic at St Thomas's Hospital in London found little evidence of secondary sexual transmission of HIV. A total of 17,829 people were tested between 1988 and 1992. Of these, 44 were found to be HIV positive, 23 of whom were infected abroad and 16 through injecting drugs use. Five HIV positives have no obvious risk factors.