Britain's needle exchanges, where drug abusers can obtain clean, free hypodermic syringes, are keeping the level of HIV infection well below the rest of Europe.

Tests show that syringe exchangers are only half as likely to be HIV-positive as other drug injectors.

Supporters of exchange schemes say these figures explode the myth that exchanges only encourage drug abuse and do nothing to halt the spread of Aids. Halting the spread of the virus through drug-injectors, it is argued, slows the spread of the disease.

Monitoring by the Centre for Research on Drugs and Health Behavior at the Charing Cross and Westminster Medical School in London has shown strong demand for free syringes since the scheme began in 1987.

Each of the 120 exchanges in England issues up to 15,000 syringes per month. Four years ago, 28 per cent of injectors said they shared syringes. Last year, they had fallen to 21 per cent.

However, reasons given by addicts for exchanging their syringes suggest that Aids is not their prime concern.

About 900 addicts attending 19 of England's 120 exchange centres were interviewed last year for the survey. About 32 per cent said they were worried about Aids, while 41 per cent used the scheme because they could not get syringes any other way. Fourteen per cent said they could not afford syringes, and another 14 per cent said they would rather get syringes free than buy them.

However, Martin Donoghoe, research fellow at the Centre, says attendance, for whatever reason, is encouraging, because all exchanges offer drug counselling, advice about Aids and condoms.

Male drug injectors appear to be changing their syringe habits, but say they are not using condoms with their non-injecting sexual partners.

Their is great concern about these female partners, because the Aids virus transfers more easily from men to women than vice versa. Also, syringe exchanges, used mostly by men, provide new facilities for women. "We need more exchanges to provide women-only sessions and creche facilities," said Mr. Donoghoe.

Tests last year by the research centre show that 4 per cent of intravenous drug injectors not attending needle exchanges were HIV-positive, compared to 2 per cent who did attend exchanges.

Britain has a lower proportion of Aids cases than France, Germany, Italy, Spain and Holland. The latest World Health organisation figures show that Britain has 1.5 Aids cases per 100,000 population. The next lowest is Germany, with 2.6 cases per 100,000. Spain has the highest number, 5.5 per 100,000.--------