Research has consistently shown a proportion of people who become infected with hep C have not shared needles or syringes. It's widely known and understood that hep C is a much tougher virus once it's outside the body, and viral load can be very high, making contaminated blood highly infectious.
This study is nearly 10 years old now, but it's taken a long time for the implications to get through to people.
The researchers collected all the injecting equipment involved in 10 injecting settings where at least one person involved was known to have hep C. The equipment (including needles / syringes, swabs, spoons, filters, water container) was then tested for the presence of hep C. The results are as follows:
This study tried to assess the numbers of people infected by hep C without sharing needles, and found 54% of their (small) sample who fell into this group had attributed the infection to shared cookers or filters.Hepatitis C virus RNA was detected on 70% (14/20) of syringes, 67% (6/9) of swabs, 40% (2/5) of filters, 25% (1/4) of spoons, and 33% (1/3) of water samples.
These figures seemed to be replicated in this later study, that again identified shared cooker use as a high risk activity for hep C transmission.
This paper takes up their point, but highlights the role of used injecting equipment introducing the hep C virus into the mixing up process.The adjusted relative hazard of seroconversion, controlling for demographic and drug-use covariates, was highest for sharing "cookers" (relative hazard = 4.1, 95% confidence interval: 1.4, 11.8), followed by sharing cotton filters (relative hazard = 2.4, 95% confidence interval: 1.1, 5.0).
Risks associated with syringe-sharing and sharing of rinse water were elevated but not significant. After adjustment for syringe-sharing, sharing cookers remained the strongest predictor of seroconversion (relative hazard = 3.5, 95% confidence interval: 1.3, 9.9). The authors conclude that sharing of injection equipment other than syringes may be an important cause of HCV transmission between IDUs.
More studies here here and here have similar findings. The last two studies I linked to brought out some new risk factors from the stats, which was female gender and being new to injecting.We argue that, for reasons of biologic plausibility and observed behavior, simply reducing the sharing of cookers and cotton is unlikely to have a substantial impact on HCV transmission. Instead, prevention measures must focus on reducing the risks associated with drug-sharing, specifically the practices of using contaminated syringes to introduce water and apportion drugs and reusing potentially contaminated water in dissolving drugs. Increasing access to sterile syringes for both drug preparation and injection and working with drug injectors to find alternative ways to prepare and distribute shared drugs would be steps in the right direction.
This study tried to assess rates of hep C tranmission in relation to age and onset of injecting, while this study tried something similar.
It's been put forward that women and people who are new to injecting are more likely to be injected by another person. Minuscule amounts of blood are all that's needed to transmit hep C. There are a few studies around which have indicated some poor practices in staunching blood flow after injecting, including either using alcohol wipes (which can increase blood flow, causing the hep C virus to leach through onto fingers) or some other inadequate material to stem the flow. Have a look here and here for more info about these poor injecting practices.
This study found increased risks in people who'd been "assisted" in injecting (eg injecting someone, holding their arm etc), and this study focused on the reasons for higher rates of hep C amongst women, including being injected by another person. This study focused on explaining the rapid acquisition of hep C in young people, new to injecting. It found that being injected by another person was one of the key variables.
So from all of that research, the take home message is:
* Avoiding the sharing of needles is not enough to prevent hep C transmission. Any shared injecting equipment can result in hep C transmission.
* Be blood aware with regards to all the other equipment involved in injecting. Invisible particles of blood are all that's need to transmit hep C. Torniquets, spoons, filters, shared water etc can all transmit hep C.
* Hand washing is likely to reduce hep C transmission, particularly if your being injected by someone / injecting someone else.
* There is not enough strong evidence that bleach will kill the hep C virus. It has a hardy outer layer that bleach may not penetrate.
* Get tested if you think you're at risk. Hep C is not a death sentence, but there are some things you can do to stay healthier if you do test positive.
* Hep C is not considered a sexually transmitted infection because it is only transmitted through blood to blood contact, and not in semen or vaginal fluid.