The sharing of injecting paraphernalia among 96 regular attenders at needle-exchange schemes in the North West of England: implications for local public health policy

Modelling the prevalence of HCV amongst people who inject drugs: an investigation into the risks associated with injecting paraphernalia sharing

BACKGROUND

In order to prevent the spread of the hepatitis C virus (HCV) amongst people who inject drugs (PWID), it is imperative that any injecting risk behaviour which may contribute to the transmission of disease has its role quantified. To inform public health organisations, mathematical modelling techniques were used to explore the risk of HCV infection through the sharing of injecting paraphernalia (including filters, cookers and water).

METHODS

A mathematical model was developed for the spread of HCV based on the injecting behaviour of PWID in Scotland, with transmission occurring through the sharing of needles/syringes and other injecting paraphernalia. Numerical simulations were used to estimate the transmission probability for HCV through the sharing of injecting paraphernalia such that the modelled endemic HCV prevalence fitted with that observed amongst PWID in Scotland.

RESULTS

The transmission probability of HCV through injecting paraphernalia was modelled to be over 8 times lower than that through needles/syringes (approximately 0.19-0.30% and 2.5%, respectively), assuming transmission occurs through a combination of at least filters and cookers. In the context of reported needle/syringe and paraphernalia sharing rates in Scotland, it is estimated that 38% and 62% of HCV infections are contributed by these practices, respectively. If needle/syringe sharing rates were to be twice those reported, the contributions would be 70% and 30%, respectively.

CONCLUSION

Given that the sharing of injecting paraphernalia among PWID is common, HCV transmission through this route could be contributing to the growing healthcare burden associated with this chronic disease. Every effort should therefore be made to establish (a) the contribution that paraphernalia sharing is making to the spread of HCV, and (b) the effectiveness of services providing sterile paraphernalia in preventing infection.

The sharing of injecting paraphernalia by intravenous drug users (IDUs) within a Worcestershire cohort, with specific reference to water and filters

Britain continues to have a drug misuse health strategy that is HIV led. Because of this, little attention has been paid to other blood-borne viruses such as hepatitis. Moreover, while the provision of needle exchange schemes has been particularly successful in containing the spread of HIV, they have had less impact on the prevalence of hepatitis within IDU cohorts. Thus, it is necessary to understand more about the potential pathways through which the hepatitis viruses can be transmitted. One way of achieving this is to assess the propensity of IDUs to share other items of injecting paraphernalia such as water and filters. In addition, it is useful to gauge the level of opinion with respect to health hazards associated with sharing such items, amongst injecting drug users. This study reports on a small pilot project initiated to assess the degree of sharing of filters and water among 40 needle exchange service users in Worcestershire. Results based on questionnaires show that sharing of water and filters is very high within the sample group. Indeed, only 10% of clients reported never sharing either water or filters. The study also demonstrates that although injectors are aware of the health risks associated with sharing (including hepatitis transmission), they continue to participate in high risk sharing activities. Moreover, the majority of IDUs questioned have a mis-conception with respect to the most hygienic sources of water for injecting. For example, only 10% consider sterile water to be the most hygienic source for injecting, with >70% considering tap water in one form or another to be safe. The study is important because it highlights the value of providing sterile water and filters to IDUs to meet their basic and fundamental needs. It is hoped that the findings from this small project will have a wider transferability to other IDU cohorts throughout the UK and beyond.