Why is injecting drug use a risk for HIV transmission?

  • Using unclean or sharing injecting drug equipment is one of the most efficient ways of transmitting HIV.
  • Reusing a needle or syringe is not the only risk; sharing other injecting equipment such as filters and water containers can also transmit HIV.

At the start of every injection, blood is introduced into the needle and syringe. Therefore, a needle and syringe that an HIV-positive person has used can contain blood with the virus in it. Transmission occurs when another person then uses the same syringe without cleaning it. The reuse of a blood-contaminated needle or syringe by another person can be an effective means of transmission because a large quantity of blood can be injected directly into the bloodstream.

Although HIV does not generally survive well outside the body, it can survive for long periods of time (over 28 days) if hermetically sealed in syringe.1 2

There is a risk of HIV infection through intravenous injecting, subcutaneous injecting (injecting into the fat under the skin) and intramuscular injection. Some injecting drug users may believe, wrongly, that they are not at risk of HIV transmission if they simply avoid intravenous injecting.

But HIV infection will not automatically occur from a single incident of shared needle/syringe use. In fact, estimates of the infection risk from an injection range from 0.63 to 2.4%.3

Two factors are likely to determine the chances of HIV infection from any single incident of shared needle/syringe use:

  • The level of HIV present in the blood injected. Very low levels of circulating virus in the blood may make HIV infection less likely. But assuming a fairly high viral load, it is thought that amounts of blood invisible to the naked eye may be sufficient to permit HIV infection.
  • The quantity of blood injected. Evidence from the follow-up of needlestick injuries and other occupational injuries involving blood shows that the likelihood of HIV infection is dose-related – the more blood injected, the more likely it is that seroconversion will take place.

But HIV infection from blood can occur in other ways as a result of injecting drug use:

  • Through sharing water used to flush blood out of a needle and syringe.
  • Through sharing syringes or 'works' that have been cleaned in a way that does not eliminate all the blood they contain.
  • Through reusing bottle caps, spoons or other containers used to dissolve drugs in water and to heat drug solutions.
  • Through reusing filters – often small pieces of cotton or cigarette filters – used to filter out particles that could block the needle.
  • Theoretically, through unsafe disposal of needles or syringes used for injecting drugs, leading to accidents in which blood gets into the body of another person.

References

  1. Abdala N et al. Survival of HIV-1 in syringes. J Acquir Immune Defic Syndr Hum Retrovirol 20(1):73-80, 1999
  2. Clay, SP et al. Survival of Human Immunodeficiency Virus (type-1) in Injection Syringes Int Conf AIDS, abstract Tu.C.2522, 1996
  3. Baggaley RF et al. Risk of HIV-1 transmission for parenteral exposure and blood transfusion. AIDS 20: 805-812, 2006
This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.
Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap
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This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.