Study: Can HIV-1-Contaminated Syringes Be Disinfected?

Throughout the course of the AIDS epidemic in the United States, injection drug use has been a major factor in the spread of HIV-1. It is an attributable risk factor for 25 percent of AIDS cases and may currently account for more than half of all new infections. Unlike other developed nations, the United States did not embrace syringe exchange programs, so prevention educators were left with the task of changing the behaviors of injection drug users (IDUs) by discouraging needle sharing and by promoting the use of bleach (sodium hypochlorite) to disinfect used syringes. Bleach soon became the standard for use in needle hygiene programs, and outreach workers distributed small bottles of bleach to IDUs around the country.

However, between 1991 and 1994, five reports combined to call into question the efficacy of bleach disinfection as a reliable AIDS prevention technique. Although no single study had been conducted that provided a complete answer on the usefulness of bleach disinfection of syringes, the combination of epidemiologic results with those from the field led to the conclusion that, in real life situations, bleached syringes might often contain viable HIV-1.

The researchers applied a sensitive HIV-1 microculture assay to determine the effectiveness of bleach in disinfecting syringes contaminated with HIV-1. The syringes were handled in the laboratory to simulate common illicit drug injection practices. When injecting into a vein, the user locates a vein and inserts the needle. To determine that the syringe is within the vein, the injector draws back to make sure blood flows into the syringe ("registering"). After the drug solution has been injected, the user often keeps the needle in the vein, refills it with blood, and re-injects it ("booting"). This practice represents a worst- case situation because what is left in the syringe is almost entirely the IDU's blood.

In their experiments, the researchers drew HIV-1-infected blood into the barrel of a 1-ml-1 insulin syringe with fixed cannula. The plunger was then depressed, either completely or partially. Syringes were recapped and stored at room temperature for up to 48 days before testing for the presence of infectious virus. The syringes were rinsed with water, 1:10 diluted household bleach, or undiluted bleach. Remaining syringe contents were extracted with cell culture media and introduced into the microculture assay. The results revealed that HIV-1 within syringes remained viable and hence potentially infectious for prolonged periods of up to five weeks at room temperature unless steps were taken to disinfect the syringe.

"This study demonstrates that in a laboratory environment designed to replicate injection behaviors, undiluted bleach is highly effective in reducing the viability of HIV-1 even after minimal contact time," the researchers wrote. "However, it did not reduce the HIV-1 recovery to zero. Furthermore, three washes with water were nearly as effective as a single rinse with undiluted bleach in reducing the likelihood that contaminated syringes harbored viable HIV-1. Given the reality that IDUs share syringes and may not have access to a new, sterile syringe for each injection, the results suggest that they should be encouraged through harm reduction interventions to clean their syringes, preferably with undiluted bleach."

The authors concluded, "We recommend that all injections, including those made by IDUs, use a new, sterile syringe. We cannot overstate the importance of increased IDU access to sterile syringes through pharmacy sales, syringe exchange programs, and physicians, as well as the removal of legal penalties for possession of syringes. Notwithstanding the caveats and cautions, the use of disinfection procedures have the potential for being life-saving in the situation when an IDU has no sterile syringes and will be using a syringe previously used by another IDU."

Back to other CDC news for January 22, 2002

Previous Updates | Search the CDC archive