Skip navigation
Centers for Disease Control and Prevention
 CDC Home Search Health Topics A-Z
Prevention Among Injection Drug Users
 IDU HIV Prevention

Archive archive

 IDU Home
 Fact Sheets:
 Syringe Disinfection
 Sterile Syringes
 Viral Hepatitis
 Subst. Abuse
 Criminal Justice
 Order Printed Materials
 Dear Colleague Letters
 Other Publications
 Safe Community Syringe Disposal
Explore IDU Topics
Link to a PDF document Link to a PDF document
Link to a Non-CDC site
Link to non-CDC site or document and does not necessarily represent the views of CDC
Adobe Acrobat (TM) Reader needs to be installed on your computer in order to read documents in PDF format. Download the Reader.
U.S. Department of Health and Human Services

Archival Content: 1999-2005

A Comprehensive Approach:
Preventing Blood-Borne Infections Among Injection Drug Users

Risk Behaviors Associated with Infection by HIV and Other Blood-borne Infections


The process of preparing and injecting drugs and the various items of equipment used provide many opportunities for contamination with and transmission of HIV or other blood-borne viruses (AED, 1997).

To be injected, drugs such as heroin must be dissolved in water. Heat is sometimes used to speed the process. This is typically done in a spoon or a bottle cap, called a "cooker."The drug and water solution is then drawn into a syringe through a filter or a "cotton", which prevents small particles in the solution from clogging the narrow gauge needle.

Before injecting intrave nously, an IDU must determine whether the needle is in a vein. To do so, he or she pulls back the syringe plunger to see if blood enters the syringe. This is called "registering". If blood registers, the needle is in a vein. Registering contaminates the entire syringe with blood: needle, hub, barrel, and plunger (Koester, 1998; Normand et al., 1995).

Once the user registers that the needle is in a suitable vein, the drug is injected directly. To ensure that all the drug is injected, the IDU may pull the plunger back several times, drawing blood into the syringe each time, and then re-injecting it. This technique, called "booting", increases the presence of residual blood in the syringe (Koester, 1998; Normand et al., 1995).

HIV survives in the residual blood in used syringes, even if it has been rinsed with water. A recent study showed that HIV in used syringes remained viable and infectious at room temperature for more than 4 weeks (Abdala, 1999).

After injecting the drug, the IDU rinses the syringe with water to prevent any remaining blood from clotting. This contaminates the rinse water. Drug injection may take place in locations with little access to water, so rinse water may be reused and therefore become increasingly contaminated. In many cases, this water is used for dissolving drugs to be injected as well as for rinsing. In the absence of a sufficient supply of new sterile syringes, IDUs must reuse their syringes. Disinfecting used syringes with bleach is recommended as a risk reduction measure, but even if done correctly, it is not as safe as using a new, sterile syringe. In reality, the multiple steps involved in the bleaching procedure and the difficulty of adequately cleaning the hard-to-reach internal spaces of a syringe mean that many IDUs are unable to properly disinfect their used syringes. (Gershon, 1998; Gleghorn et al., 1994; McCoy et al., 1994).

The patterns of cocaine and heroin use present particular viral transmission risks (Koester et al., 1996). The desire and need for cocaine mean that users of this drug inject frequently, multiplying the opportunities for transmission of blood-borne viruses. Heroin injectors make fewer injections per day, but their risks are multiplied because of their over whelming physical and emotional need to avoid the withdrawal syndrome. Their objective is to inject as soon as possible after obtaining the drug, which means they may use whatever syringe or equipment is closest to hand, whether or not that presents viral infection transmission risks (Koester et al., 1996).

Transmission of HIV and other blood-borne viruses can occur through either direct or indirect sharing of contaminated equipment. Direct sharing involves injecting drugs with a syringe already used by another injector. Indirect sharing occurs when injectors prepare their own drugs but use injection paraphernalia, such as water, cookers, cottons, and spoons, that others have used, or when injectors jointly prepare and share drugs (Koester and Hoffer, 1994). This occurs, for example, when several IDUs pool their money to purchase drugs together. The entire amount of drug is dissolved during a shared preparation process. The preparer draws all the drug and water solution into a syringe through the cotton. Using the calibrations on the syringe, the preparer then transfers individual doses of the drug into the syringes of the other users. After injecting the drug, users rinse their syringes with water. Though syringes themselves are not used by more than one person in indirect sharing, they still become contaminated with blood because of contact with contaminated ancillary paraphernalia.

Other practices associated with indirect sharing can also transmit infection, including (Koester and Hoffer, 1994):

  • Squirting the drug solution from a previously blood-contaminated syringe into the cooker or spoon and then drawing it into another syringe.
  • Using the plunger from a previously blood-contaminated syringe to mix the drug with water.
  • Returning the drug solution from a previously blood-contaminated syringe to the shared cooker or directly to another syringe. This occurs when the user draws up more than his or her allotted share of the drug.
  • "Beating", or pressing, a used cotton (or several cottons) to retrieve any drug remaining in the cotton from a previous injecting session.
  • "Kicking out a taste" by putting a part of the drug/water solution from a previously blood-contaminated syringe back into the cooker or into another IDU's syringe so that another or several other IDUs can get some of the drug.
  • Drawing up the water for dissolving the drug by using another injector's used and inadequately disinfected syringe.

High-risk drug useAnother attribute of drug use that contributes to the risk of viral transmission is the use of more than one drug. For example, IDUs often use alcohol, cigarettes, and marijuana in addition to the drug they inject (AED, 1997). "Speedball", a combination of heroin and cocaine is favored by some injectors, and has been highly correlated with HIV infection (Battjes et al., 1994). Common reasons for this polydrug use include the need to counteract the effects of one drug with another, the desire to experience the effects of more than one drug, and the need to substitute when the drug of choice is too difficult or costly to obtain. Polydrug use can increase the risk of HIV and other blood-borne disease transmission in several ways. For example, the situations and people with whom an IDU uses drugs may vary depending on the drug. These differing contexts may expose the individual to a variety of high-risk situations. Furthermore, intoxication with one drug may lessen an individual's ability or desire to reduce risks associated with the use of another drug.


High-risk drug use behaviors and high-risk sexual behaviors are often linked, further increasing the risk of HIV and other blood-borne diseases being transmitted from one person to another (Chuet al., 1998). These risky sexual behaviors include unprotected anal, vaginal, or oral sex; multiple partners; and lack of treatment of sexually transmitted diseases (STDs), especially those with ulcerative lesions. These high-risk drug and sexual behaviors intersect in a variety of ways to increase risk. For example, sex partners of HIV-infected IDUs may begin injecting drugs themselves (Ouellet et al., 1998). Drug injectors who also frequently smoke crack cocaine tend to spend time in crack houses or other places with other drug-injecting cocaine users (Friedman et al.,1995). Crack use is associated with high-risk sexual activities, possibly because of the disinhibiting effect of the drug or because of the addicted person's need to obtain the drug, which leads to exchanges of sex for crack or for money to buy crack (Edlin et al., 1994). Many IDUs, both men and women, trade sex for drugs or money to buy drugs or engage in commercial sex or hustling to generate income for their habits and this increases their transmission risks (AED, 1997; Kail et al., 1995; Rietmeijer et al., 1998; Schilling et al., 1992).

View PDFPDF Icon

Previous Page | Table of Contents | Next Page

This CDC Web site is no longer being reviewed or updated and thus is no longer kept current. This site remains to assist researchers or others needing historical content.

Go to top

Privacy Policy | Accessibility The U.S. Government's Official Web Portal