always using disinfectants. A follow-up study by these investigators reexamined this result (Vlahov et al., 1994), using a larger sample size and examining the influence of potentially confounding variables on the study outcome, including the effect of drug-use variables, the possibility of sexual acquisition of HIV infection (Solomon et al., 1993), and the potential for study participants to provide socially desirable responses to the investigator's questions concerning disinfection practices (Latkin et al., 1993). Nevertheless, similar null results were obtained, with injection drug users who reported using disinfectants all the time compared with those who reported no use of disinfectants (Vlahov et al., 1994). Thus, bleach use, as practiced in Baltimore in the early 1990s, did not eliminate or substantially reduce the risk of HIV seroconversion among injection drug users who reported using it all the time.
Similar findings were subsequently found in New York (Titus et al., 1994), in a case-control study. After adjusting for possible confounders, no evidence that bleach use protected against incident HIV infection was reported. Another study of HIV seroconversion among injection drug users in San Francisco showed no protective effect with bleach disinfection (Moss et al., 1994). It remains to be established whether these disappointing results derive from exaggerated reporting of injection drug users about their actual disinfection practices, the use of inadequate disinfection methods, contamination of water or ancillary injection paraphernalia with HIV, or the inability of bleach or alcohol to effectively disinfect contaminated needles and syringes within the context of their actual use by injection drug users.
Responding to concerns arising from laboratory studies about prevailing methods for bleach inactivation of HIV and epidemiologic studies that suggest little, if any, protective effect of needle and syringe disinfection efforts, the Centers for Disease Control, the National Institute on Drug Abuse, and the Center for Substance Abuse Treatment (CSAT) sponsored a meeting in February 1993 at which the current status of bleach outreach and research was reviewed. Discussions from this meeting provided the basis for the publication of provisional guidelines on bleach disinfection (Curran et al., 1993). These published guidelines included the following recommendations:
Cleaning should be done twice—once immediately after use and again just before reuse of needles and syringes.
Before using bleach, wash out the needle and syringe by filling them several times with clean water. (This will reduce the amount of blood and other debris in the syringe. Blood reduces the effectiveness of bleach.)
Then, use full-strength liquid household bleach (not diluted bleach).
Completely fill the needle and syringe with bleach several times. (Some suggest filling the syringe at least three times.)