Monitoring injecting drug users risk behaviours is important because changes in these can rapidly increase blood-borne virus transmission rates. In England and Wales needle and syringe sharing in the previous month has been monitored through annual cross-sectional surveys since 1991. After declining in the early 1990s, the proportion sharing increased significantly between 1997 and 2000. This, and an apparent increase in hepatitis B transmission, indicates that injectors are at an increasing risk of infection with blood-borne viruses.
Needle and syringe (direct) sharing by injecting drug users (IDU) has been recognized since the early 1980s as a route for the transmission of HIV. In response many countries introduced harm-reduction interventions, such as methadone prescribing and needle and syringe exchange. Countries such as the UK, which promptly introduced a comprehensive intervention programme, have low or declining HIV prevalences among IDU [1,2]. The monitoring of IDU is important because changes in drug use and injecting risk behaviour can rapidly increase HIV transmission rates, as occurred in Canada [3,4].
In England and Wales, data on direct sharing has been collected from IDU in contact with a sample of drug services since 1991 , and on other (indirect) sharing practices, such as sharing spoons and filters, since 1996 . Clients of collaborating services, who have ever injected drugs, are asked to participate. Those who consent provide an oral fluid sample, for anti-HIV, anti-hepatitis B core (HBc) and anti-hepatitis C virus (HCV) testing,  and complete a brief questionnaire . Statistical analyses were undertaken in SPSS.
Between 1991 and 2000 there were 21 161 participations by current injectors (IDU who had injected in the preceding month) out of a total of 30 806 participations. Of the participations by current injectors, 22% (4646/20 786) were women, 34% (6977/20 484) were aged under 25 years, and 20% (4181/21 161) were recruited in London. In 2000 the prevalences of anti-HIV, anti-HBc and anti-HCV among current injectors were 0.8% (20/2488), 20% (490/2487) and 31% (775/2488), respectively.
Direct sharing in the previous month changed over time; after an initial decline in the early 1990s there was a significant increase between 1997 and 2000, from 21% (71/337) to 41% (123/298) in London, and from 17% (237/1431) to 29% (549/1886) elsewhere (Fig. 1). These changes remained after adjustment for covariates (age, sex and recruitment location) using multivariable logistic regression (Fig. 1).
The increase in sharing between 1997 and 2000 was seen in both men, from 16% (218/1367) to 28% (478/1683), and women, from 23% (90/393) to 39% (191/485), and across all age groups, from 25% (121/485) to 31% (187/606) in under 25 year olds, from 17% (148/885) to 31% (326/1067) in 25–34 year olds, and from 9% (30/349) to 31% (149/479) in those over 34 years of age.
The proportion of current IDU reporting indirect sharing was found not to have changed since measurement started in 1996, and in 2000 was 62% (193/310) in London and 53% (1055/1976) elsewhere.
To explore the impact of the increase in direct sharing on blood-borne virus transmission the prevalences of anti-HBc and anti-HCV among recent initiates (those current injectors who had started injecting in the past 2 years) were examined. An increase in the prevalence in this group over time would be suggestive of an increase in incidence. The anti-HBc prevalence among this group increased significantly between 1997 and 2000, from 2.9% (13/449) to 6.7% (41/614) χ2df = 1(forlinearassociation) = 7.100, P = 0.008, whereas that for anti-HCV did not change between 1998 (8.1%, 48/595) when testing started and 2000 (8.5%, 52/614). The anti-HIV prevalence was very low among this group and so could not be examined (overall prevalence during the period 1997–2000 was 0.18%, 4/2278).
This increase in direct sharing among IDU and the increase in the prevalence of hepatitis B among recent initiates suggests that those who inject drugs may be at increasing risk of infection with blood-borne viruses. The significance of these increases depends upon the representativeness of our survey. The marginalization and illegality of drug injecting, however, impede the construction of a sampling frame. As this survey was recruited from a wide range of locations and service types using a consistent methodology over time it is likely to be representative of IDU in contact with services. The existence of the increase in the risk of infection is supported by a rise in the annual number of acute hepatitis B reports associated with injecting drug use (Fig. 1) .
This increase in sharing may lead to increased HIV transmission; however, the prevalence of HIV among current IDU in England and Wales is very low and appears not to have changed in recent years [6,8]. This low prevalence and the selective nature of sharing, with injectors tending to share only with their sexual partners or close friends , suggest that although opportunities for HIV transmission through injecting are likely to have increased, actual transmission probably remains rare.
Indirect sharing is thought to play a much greater role in the transmission of hepatitis C than HIV and hepatitis B . The stable prevalence of hepatitis C may therefore be related to the fact that the proportion of injectors reporting indirect sharing has not changed over time.
This study did not investigate reasons as to why direct sharing has increased; this increase has, however, occurred at a time of increased sexual risk behaviours [11,12], which have been attributed to changed perceptions of the severity of HIV infection following advances in treatment. Other possible explanations include IDU no longer perceiving themselves to be at high risk of infection, and increased constraints on the availability of sufficient clean needles and syringes.
IDU risk-reduction strategies are, however, complex and fluid, and can include the cleaning of works before re-use and being selective about sharing/injecting partners . Changes in these behaviours are not currently monitored, as methods for measuring these need further development .
The importance of the coverage of needle and syringe provision has been shown by the increase in HIV prevalence among IDU in Vancouver, a city with a large established needle exchange programme . This rise has been associated, at least partly, with an increase in injection frequency (as a result of a growth in cocaine use) that was not matched by an increased supply of needles and syringes . In the United Kingdom the coverage of needle and syringe distribution is not known, although it has been estimated that 25 million syringes were distributed in 1997 after a decade of service expansion . Service development has continued with the implementation of a national strategy for reducing problem drug use , although with a focus on improving access to treatment.
The findings presented here suggest that the ongoing provision of needle exchange, and other harm-reduction measures, may not be sufficient to maintain reductions in risk behaviour. If low HIV prevalences among IDU are to be sustained then interventions to maintain the reduction in direct sharing, as well as measures to ensure adequate service coverage, may need development.
V.D. Hope, L. Jordan and T. Paine were responsible for the day-to-day co-ordination of the survey. O.N. Gill manages the survey and, with J.V. Parry, was involved with its design. Laboratory work was undertaken by S. Barnett. Analysis was undertaken by P. Rogers assisted by V.D. Hope. All authors contributed to the writing of the paper, with V.D. Hope leading.
The authors would like to thank all the drug services who collaborated with the survey and all the injectors who took part. They would also like to thank Shona Livingstone for her assistance with the preliminary statistical analyses. This survey of IDU is part of the Unlinked Anonymous Prevalence Monitoring Programme, which is funded by the Department of Health.
1.Hurley SF, Jolley DJ, Kaldor JM. Effectiveness of needle-exchange programmes for prevention of HIV infection.Lancet
2.Stimson GV. AIDS and injecting drug use in the United Kingdom, 1987–1993: policy response and the prevention of the epidemic.Soc Sci Med
3.Patrick DM, Strathdee SA, Archibald CP, Ofner M, Craib KJP, Cornelisse PGA, et al.Determinants of HIV seroconversion in injection drug users during a period of rising prevalence in Vancouver.Int J STD AIDS
4.Strathdee SA, Patrick DM, Currie SL, Cornelisse PG, Rekart ML, Montaner JS, et al.Needle exchange is not enough: lessons from the Vancouver injecting drug use study.AIDS
5.Durante AJ, Hart GJ, Brady AR, Madden PB, Noone A. The health of the nation target on syringe sharing: a role for routine surveillance in assessing progress and targeting interventions.Addiction
6.Unlinked Anonymous Surveys Steering Group. Prevalence of HIV and hepatitis infection in the United Kingdom 2000.Annual report of the Unlinked Anonymous Prevalence Monitoring Programme.
London: Department of Health, 2001.
7.Allwright S, Bradley F, Long J, Barry J, Thornton L, Parry JV. Prevalence of antibodies to hepatitis B, hepatitis C and HIV in Irish prisoners: results of a national cross sectional survey.BMJ
8.Judd A, Hunter GM, Maconochie N, Hickman M, Parry JV, Renton AM, et al.HIV prevalence and risk behaviour among female injecting drug users in London, 1990 to 1996.AIDS
9.Rhodes T, Quirk A. Drug users sexual relationships and the social organisation of risk: the sexual relationship as a site of risk management.Soc Sci Med
10.Coutinho RA. HIV and hepatitis C among injecting drug users – success in preventing HIV has not been mirrored for hepatitis C.BMJ
11.Dodds JP, Nardone A, Mercey DE, Johnson AM. Increase in high risk sexual behaviour among homosexual men, London 1996–8: cross sectional questionnaire study.BMJ
12.Johnson AM, Mercer CH, Erens B, Copas AJ, MacManus S, Wellings K, et al.Sexual behaviour in Britain: partnerships, practices, and HIV risk behaviours.Lancet
13.Hunter GM, Stimson GV, Judd A, Jones S, Hickman M. Measuring injecting risk behaviour in the second decade of harm reduction: a survey of injecting drug users in England.Addiction
14.Schechter MT, Strathdee SA, Cornelisse PGA, Currie S, Patrick DM, Rekart ML, et al.Do needle exchange programmes increase the spread of HIV among injection druug users?: an investigation of the Vancouver outbreak.AIDS
15.Hope VD, Judd A, Hickman M, Lamagni T, Hunter G, Stimson G, et al
. Prevalence of hepatitis C virus in current injecting drug users in England and Wales: is harm reduction working?Am J Pub Health
16.Tackling drugs to build a better britain: the Government's ten-year strategy for tackling drug misuse. London: Stationary Office, 1998.