Sharing Drug Injection Equipment

The use of nonsterile injection equipment may account for a range of infections in IV drug users, including bacterial endocarditis, hepatitis, malaria, and cellulitis or soft tissue infections (Louria et al., 1967). As the number of people with whom injection equipment is shared increases, so does the risk of HIV infection (Chaisson et al., 1987b). As with other blood-borne infections to which IV drug users are prone, HIV spreads from the infected to the uninfected user primarily by the sharing of blood-contaminated injection equipment, which serves as the vector of the virus.

IV drug users share injection equipment for a variety of reasons: pragmatically, clean "works" (the collective term for injection paraphernalia) are scarce; legally, the possession of injection equipment is a criminal offense in many states; socially, sharing represents a form of social bonding among IV drug users (Friedman et al., 1986). Before describing the injection behaviors associated with transmission, we discuss the setting in which drug use occurs.

Frequency Of Injection

Another factor associated with HIV infection is the frequency of injection: those who inject drugs frequently are more likely to be seropositive than those who inject less often (Blattner et al., 1985; Des Jarlais, 1987b). Some IV drug users are hard-core addicts who inject drugs many times every day; some are otherwise successful middle-class users who inject less frequently. Still other IV drug users inject many times a day for a few months and then stop; some others inject only a few times a year.³

The sharing of injection equipment appears to be common behavior in both IV drug users who inject frequently and in those who inject less often (Friedland et al., 1985). However, more frequent injections are likely to mean more episodes with shared equipment, thus increasing the likelihood of HIV infection. In addition, for IV drug users who are addicted, the symptoms of drug withdrawal can heighten the sense of urgency or desire for the drug and decrease the likelihood that safer injection practices will be used. Finally, whether an IV drug user did most of his or her injecting prior to 1975 or later will greatly affect his or her risk of HIV infection. Other important variables in determining the risk of HIV infection include the prevalence of infection in the local population, the number of people who practice needle-sharing, the number and frequency of injections, and the injection route (intravenous, intramuscular, or subcutaneous).

Polydrug Use

One consistent finding with significant implications for treatment and prevention efforts is that of multiple drug use among those who inject drugs. Studies of treatment populations (B. D. Johnson et al., 1985; Ball et al., 1986) suggest that a majority (60-90 percent) of IV heroin users report regular use of at least one other nonopiate. (A survey of approximately 100 former heroin users enrolled in methadone maintenance clinics in the New York City area found that 91 percent also reported IV cocaine use [Brown and Primm, 1988].) The choice of drugs for injection varies among different drug subcultures and over time. Heroin was the dominant injected drug a few years ago, but today, IV drug users may also inject cocaine, heroin and cocaine in combination, or a variety of other drugs, including amphetamines (Black et al., 1986).

Cocaine has been linked to HIV infection in New York City and San Francisco (Chaisson et al., 1988; Friedman et al., 1988). Among 673 IV drug users surveyed in San Francisco, IV cocaine use significantly increased the risk of HIV infection (Chaisson et al., 1988). Unfortunately, to date, some forms of drug treatment, including methadone, have not been effective for cocaine dependency. Indeed, Chaisson and colleagues (1988) found that 26 percent of cocaine users who were already in long-term methadone treatment began injecting cocaine after they entered treatment. Injection practices also appear to vary for different drugs. With cocaine's shorter-lived "high," IV drug users who shoot cocaine may inject themselves repeatedly until their supply is exhausted—thus injecting themselves more frequently than if they were using heroin alone.⁴

Cocaine is associated with HIV infection in several ways. When cocaine is injected with nonsterile injection equipment, it poses the risk of blood-borne HIV infection. When it is smoked (as "crack"), it can be associated with high-risk sexual activity because crack frequently heightens perceptions of sexual arousal (Friedman et al., 1988). Like heroin, it can be used at or near the site of purchase in so-called "crack houses." Unlike heroin, however, crack is cheap and relatively easy to use, and any evidence of its possession is easily obliterated—factors that have probably contributed to its popularity (Inciardi, 1987). The use of crack can result in increased risk of HIV infection owing to decreased sexual inhibitions and an increased desire for drugs. Outreach workers in Harlem report finding women and girls (some only in their early teens) who are engaging in unprotected intercourse in exchange for either money or crack (Friedman et al., 1988). Moreover, ethnographic data reported by Friedman and colleagues (1988) indicate that crack use among women can lead to prostitution, which in turn can lead to heroin use, thus amplifying among these women the risk of acquiring and spreading HIV infection.

Sexual Behaviors And IV Drug Use

As of November 14, 1988, CDC (1988) reported 3,359 cases of AIDS that were attributed to heterosexual transmission. Of the total cases, 2,154 (64 percent) were people who reported heterosexual contact with a person with AIDS or a person at risk of AIDS. The other 1,205 (36 percent) were people who reported no other risk-associated behavior but were born in countries in which heterosexual transmission has played a key role in the spread of the virus. The vast majority of the cases that have been diagnosed among those born in this country is thought to be associated directly with IV drug use or with sexual contact with an IV drug user (Brown, 1988).⁵ Yet less is known about the dynamics of heterosexual HIV transmission from IV drug users than about transmission from index cases in hemophiliac, transfusion recipient, or bisexual male populations. The general efficiency of heterosexual HIV transmission is not known, but it seems likely that the prospects for understanding this dimension of the epidemic would be improved if attention were directed toward the most frequent occurrence of the phenomenon: sexual transmission related to the IV drug-using population.

In the past, drug-use behaviors in the IV drug-using population received more attention than sexual behaviors; now, however, sexual behaviors have become the focus of recent studies, which are providing some insight into the range of behaviors that occurs. Surveys of IV drug users who had recently entered methadone treatment programs (in New York City; northern New Jersey; San Antonio, Texas; and Los Angeles, California) found that more AIDS prevention measures were being taken with respect to drug use than with respect to sexual activity: only 14 percent of the respondents in these studies reported that they had begun or increased condom use (Battjes and Pickens, 1988). In another study (Primm et al., 1988), more than half (60 percent) of the IV drug users' sexual partners did not inject drugs; however, male respondents were more likely than female respondents to report a noninjecting sex partner. Only 5 percent of the study participants reported condom use; among this 5 percent, condoms were used in only 35 percent of all sexual encounters.

Sexual behavior and drug use are topics that are often investigated separately by researchers whose careers have focused on one or the other activity. Yet sex and drug use are apt to be inextricably linked, and the nexus between these two most private activities is a critical area for AIDS research. In certain contexts, sexual behavior cannot be separated from drug use. For example, among female IV drug users who are the sexual partners of male IV drug users, sex is often used to obtain drugs or is an aspect of a relationship based on drug use. A social structure that supports male dominance may make it difficult for women to propose behavioral changes (to say "no" to sex, to use condoms, or to refrain from certain types of sex). Women who are financially dependent on men or who exchange sex for money or other necessities of life may face the dilemma of choosing between economic survival and unsafe sex (Worth, 1988).

Data from samples recruited through drug treatment programs, such as the Treatment Outcome Prospective Study or TOPS (see foonote 19 in this chapter), find that the bulk of the active drug-using population consists of young men (Ginzburg, 1984). Indeed, men constitute 74 percent of treatment admissions for heroin use. Women constitute a proportionately smaller group, although over the last decade the problem of drug addiction among women "is one of large and growing proportions" (Cuskey and Wathey, 1982). Nevertheless, women are often omitted or seen as peripheral in ethnographic accounts of the heroin world, and studies of female IV drug users are rare (Rosenbaum, 1979a). The links among IV drug use, heterosexual transmission, and perinatal infection may bring further attention to women who are at risk of AIDS through IV drug-related behavior. A review of the 1,819 women who were diagnosed as having AIDS between 1981 and 1986 (Guinan and Hardy, 1987) found that the majority of these women reported IV drug use. The second most common AIDS risk factor for women is heterosexual contact with a person at risk for AIDS. Indeed, Wofsy (1987) has estimated that as many as 20,000 women whose sexual partners are IV drug users may be infected with HIV.

According to Des Jarlais and colleagues (1984), as many as 80 percent of male IV drug users are in a primary relationship with women who do not themselves use drugs; female IV drug users, on the other hand, are apt to be partnered with male drug users. Thus, women are at risk of HIV infection that is both directly and indirectly associated with IV drug use. While some information on female IV drug use is available from women entering drug treatment, little is known about women who are involved in intimate relationships with male IV drug users.

Ethnographic studies of female IV drug users at the Stuyvesant Polyclinic and the Montefiore Medical Center in New York City (Wofsy, 1987; Worth, 1988) have found that proposals to change sexual practices (including the use of condoms) require redressing the balance of power within intimate relationships. For these women, asking a man to use a condom provokes the fear of breaching relations that may fulfill the woman's sexual, personal, financial, and drug needs.

As discussed in Chapter 2, prostitutes are at risk of acquiring HIV infection through both sexual and drug-use behaviors. A 1987 survey of street prostitutes in the New York City area indicated that approximately one half had injected drugs at least once and one third had injected drugs at some time during the previous two years (Des Jarlais et al., 1987). The prevalence of unprotected intercourse among prostitutes varies with the context of the sexual encounter; safer sex is practiced by female prostitutes in professional relationships more often than in personal ones (Cohen, 1987; Darrow et al., 1988). The prostitute population is worthy of further attention, as male and female prostitutes are at risk of being infected by and of spreading infection to their sexual partners, both professional and personal, as well as to their offspring.

Because of the link between IV drug use and perinatal transmission of HIV, information is needed about contraceptive and childbearing behaviors in the IV drug-using population. Unfortunately, currently available data permit only a rudimentary picture of these behaviors. Despite heroin's capacity to suppress fertility to a certain extent in women, Cuskey and Wathey (1982) found that, in New York City, birth rates for addicted women were higher than those for nonaddicted women. Others (Densen-Gerber et al., 1972; E. M. Johnson, 1987) have reported an association between drug use and promiscuity and prostitution. Women who use intravenous drugs may also be poor users of contraception. In a study that matched women on age, ethnicity, and marital status, Ralph and Spigner (1986) noted that contraception was less frequent among female addicts than among nonaddicted women. The importance of these data becomes apparent in view of the fact that perinatal HIV transmission can occur if the mother is infected. With the majority of women with AIDS in their childbearing years (CDC, 1987a), offspring of IV drug users may constitute a growing proportion of future cases of HIV infection.

Toward A Better Understanding Of Risk-Associated Behaviors

Intravenous drug use comprises a complex set of behaviors that are enacted in diverse social situations. Drug use is a social problem that is rooted in a network of other problems; most students of drug use believe that only complex, far-reaching solutions that take into account all aspects of that network will ultimately be effective. Such solutions require the attention of a range of agencies—law enforcement, social service, health, housing, and education. Programs that address the individual in the context of peers, family, and community and those that focus on the multiple factors that influence drug use hold the most promise. Solutions to the problems of drug use will also require the attention of a range of disciplines. Many questions that will arise can best be answered by the social and behavioral sciences; others will require the expertise of pharmacology, toxicology, and other biomedical sciences. In addition, knowledge is needed on how addiction occurs and on the biological factors that influence drug use, addiction, cessation, and relapse. Finally, mechanisms to improve collaboration and coordination among those seeking solutions will be required for effective action. The committee thus recommends that high priority be given to studies of the social and societal contexts of IV drug use and IV drug-use prevention efforts.

The dynamics of IV drug use—injection behaviors, drugs of choice, and sexual and contraceptive behaviors—vary over time for each drug user. They also vary across cultures and geographic locations, as well as by age, race, gender, and ethnicity. These variations have important implications for the spread of HIV that cannot be captured by or understood through cross-sectional studies that provide only a "snapshot" view of evolutionary and variable behaviors. It will be necessary to make a long-term commitment to a diversified behavioral research portfolio on IV drug use with sufficient support to sustain these efforts. Multiple, prospective longitudinal studies are needed to keep abreast of problems and changes as they occur.

Studies that seek to understand sensitive, private behaviors pose formidable but not insurmountable challenges. That it is worthwhile to devote the necessary resources to meet these challenges is indisputable: the public health benefits to be gained, particularly for ethnic and racial minority populations, are great. As discussed in the final section of this chapter, research has consistently shown that racial and ethnic minorities bear a disproportionately large burden of morbidity and mortality associated with HIV infection.

Information is urgently needed about IV drug-use patterns and how injection behaviors vary by age, race, sex, ethnicity, sexual orientation, and other demographically significant variables. (For example, women and men report quite different reasons for initiating drug use, and they also report different patterns of use [Burt et al., 1979; Rosenbaum, 1981; E. M. Johnson, 1987].) Knowledge is also needed about how people enter and exit the IV drug-using population, the conditions under which individuals progress from sniffing or smoking injectable drugs to shooting them, how needle-sharing behaviors are initiated and sustained, and how to intervene effectively in these dangerous practices. The committee recommends that high priority be given to research on the natural history of IV drug use, with an emphasis on prospective longitudinal studies of the factors associated with initiation into and cessation of IV drug use.

As stated earlier, IV drug-use behaviors convey the risk of HIV infection to sexual partners and offspring. Unfortunately, how sexual and contraceptive behaviors vary and are distributed within the heterogeneous IV drug-using population are incompletely understood. Although projected estimates of future HIV infection rates are subject to considerable variation, it is likely that a significant proportion of heterosexually and perinatally acquired infection will come from the IV drug-using population. Therefore, the committee recommends that high priority be given to studies of the sexual and procreative behavior of IV drug users, including methods to reduce sexual and perinatal (mother-infant) transmission of HIV.

Implementing the recommendations offered in the preceding paragraphs will provide the information necessary to understand some of the drug-use behaviors that transmit HIV. Yet understanding is only the first step in controlling the spread of disease. Collecting data on dynamic, risk-associated behaviors requires a long-term commitment; thus, research should proceed as efforts are being made to facilitate HIV risk reduction among IV drug users.

Changes In Injection Behavior

The first risk reduction studies among IV drug users were conducted in New York City, where signs of infection were noted early in the epidemic and where the greatest number of AIDS cases has occurred. Ethnographic interviews conducted in New York in the fall of 1983 among IV drug users who were not in treatment indicated that these drug users were aware of AIDS. Data from this study also indicated that many people knew the virus was transmitted through shared injection equipment, and many recognized the potential benefit of behavioral change in this practice (Des Jarlais et al., 1986b). This awareness of AIDS and knowledge of the routes of transmission developed prior to any AIDS prevention programs for IV drug users in New York. It reportedly arose from information transmitted through the mass media and through the informal communication networks among IV drug users in the city.

Formal interviews of methadone patients from the New York City area were conducted in the fall of 1984 (Friedman et al., 1987b). In a similar study, individuals in methadone treatment and prison detoxification programs were interviewed in 1985 and 1986 (Selwyn et al., 1987). In all of the samples, the majority of respondents reported some form of AIDS risk reduction. The most commonly reported means taken to avoid HIV infection were the increased use of illicit sterile injection equipment, reduction in the number of persons with whom the respondent was willing to share equipment, and reduction or cessation of IV drug use.

In the spring of 1985, field studies of persons selling drug injection equipment in New York showed that there had been a large-scale expansion of the illicit market for sterile injection equipment, and at least part of the expansion was attributed to concerns about AIDS (Des Jarlais et al., 1985). The demand for sterile injection equipment was so great, in fact, that counterfeit sterile needles and syringes were being sold: needles and syringes that had been used were rinsed out and replaced in their original packages, which were then resealed and sold as unused.

The state of New Jersey began an ex-addict outreach program in the fall of 1985 (Jackson and Neshin, 1986; Jackson and Rotkiewicz, 1987). The program trained ex-addicts as AIDS educators, who then went into the IV drug-using community and taught current IV drug users about AIDS: how it is transmitted and how to decontaminate used injection equipment by boiling the equipment in water or soaking it in bleach or alcohol. Many IV drug users reported that they found instruction in sterilizing injection equipment to be useful. However, somewhat to the surprise of the designers of the program, a common response of those users reached by the ex-addicts was a desire to reduce the risk of AIDS by entering drug treatment and reducing or eliminating drug injection behavior. The state responded by establishing a program in which the ex-addict outreach workers distributed vouchers that could be redeemed for a period of free detoxification treatment. (Normally, this treatment would have cost the IV drug user $50-$75.) More than 85 percent of the vouchers were redeemed by IV drug users for detoxification treatment.

In 1987 reports were published on the increasing use of the syringe exchange program in Amsterdam (van den Hoek et al., 1987; Buning et al., in press) and the bleach distribution program in San Francisco (Chaisson et al., 1987a; Watters, 1987a). The Amsterdam program had actually been established prior to concerns about AIDS, but it was greatly expanded when AIDS cases were diagnosed in the city. Contrary to popular belief, the expansion of the program—from the distribution of 25,000 sterile needles and syringes in 1984 to 700,000 sterile needles and syringes distributed in 1987—did not lead to an increase in the number of IV drug users in the city or to a decrease in the number of IV drug users entering drug treatment (Buning et al., 1988, in press). In another study conducted in Amsterdam (van den Hoek et al., 1987), increased use of the needle exchange program occurred simultaneously with reductions in the reported frequency of drug injection among the respondents.

The bleach distribution program in San Francisco involved community health outreach workers who distributed small bottles of full-strength household bleach. The instructions on the bottle stated that needles and syringes should be rinsed twice with the bleach and then twice with clean water. This procedure could be carried out very quickly (as compared with the previously recommended 10- to 15-minute procedure of soaking a needle and syringe in a 10 percent bleach solution). A large number of IV drug users in San Francisco—one half of the subjects in one study (Chaisson et al., 1987a) and two thirds of the respondents in another (Watters, 1987a)—rapidly adopted use of the small bottles of bleach. A large-scale program of antibody testing and counseling was also being conducted at the same time as the bleach distribution campaign. Either one or both of the programs together may have caused behavioral change or at least sensitized IV drug users to the need for such change (Moss and Chaisson, 1988).

Other studies reported in 1987 indicate some limitations on the AIDS prevention efforts aimed at IV drug users. An evaluation of an ex-addict outreach program in Baltimore showed that IV drug users in the city were changing their behavior to reduce the risk of AIDS; however, the change could not be attributed to the efforts of the outreach workers (McAuliffe et al., 1987). A study in Sacramento, California, found that knowledge of AIDS by itself did little to change the risk behavior of IV drug users in that city; most continued to engage in high-risk behavior, even though they were aware of how AIDS is transmitted and believed that they would become exposed if they continued the behavior (Flynn et al., 1987). In this sample, information and even perceived self-susceptibility were insufficient to alter behavior.

A number of studies of AIDS risk reduction have been reported in 1988. Table 3-1 notes these efforts, as well as other recent AIDS risk reduction research. The topics of these studies include risk reduction associated with entry into methadone maintenance treatment (Abdul-Quader et al., 1987; Ball et al., 1988; Blix and Gronbladh, 1988; Hartel et al., 1988; Yancovitz et al., 1988), syringe exchange programs (Alldritt et al., 1988; Buning et al., 1988, in press; Hart et al., 1988; Ljungberg et al., 1988; van den Hoek et al., 1988b), purchasing sterile injection equipment at pharmacies (Espinoza et al., 1988; Fuchs et al., 1988; Goldberg et al., 1988), information campaigns (Bortolotti et al., 1988; de la Loma et al., 1988), and counseling with antibody testing (Hemdal, 1986; Bottiger et al., 1988; Casadonte et al., 1988; Gibson et al., 1988; Moss et al., 1988a; Olin and Kall, 1988; van den Hoek et al., 1988a), as well as many studies in which the mechanism of change was not specified.

TABLE 3-1

Recent Studies of AIDS Risk Reduction and the Prevention of HIV Transmission Among IV Drug Users.

There are now enough studies of AIDS risk reduction among IV drug users to derive some generalizations that describe the current state of knowledge. First, it is quite clear that IV drug users will modify their behavior to reduce their risk of AIDS. Although the studies that support this conclusion tend to rely heavily on self-reported behavioral modifications, there are enough studies in which there is some independent evidence of change to conclude that the self-reports reflect what has actually occurred. Examples of the independent confirmation of change include the increased demand for sterile injection equipment in New York City, increased use of syringe exchange programs, and acceptance of bottles of bleach for decontamination of used injection equipment.

The second generalization that can be made is that there is wide variation in the percentage of drug users that reported AIDS risk reduction in the different studies. Percentages ranged from 85 percent in two studies in New York (Ball et al., 1988; Battjes and Pickens, 1988; Yancovitz et al., 1988) to what researchers termed ''poor'' in Madrid, Spain (de la Loma et al., 1988). Interpreting this variation is difficult for several reasons. The studies use different outcome measures that range from the increased use of sterile injection equipment to entrance into drug treatment to any self-reported change in behavior. Even when the "same" outcome measure is used in different studies, the wording of the study questionnaires may be sufficiently different as to make comparisons across studies quite difficult. Problems in interpreting the behavioral change data also arise from a lack of specification of the mechanism or "cause" of the behavioral change. Most of the studies that have been conducted did not identify causal factors; of those that did, different analytic frameworks were used to describe the mechanisms of change, which appeared to vary according to the local environment. For example, the potential effects of an AIDS education campaign in an area in which sterile injection equipment may be lawfully purchased in pharmacies cannot be compared easily with a similar campaign in an area in which legal access to and possession of sterile injection equipment are prohibited. Nevertheless, despite the problems in assessing the extent and causes of AIDS risk reduction in different geographical areas, it is still possible to conclude from the data that risk reduction has occurred, although it is highly variable. Unfortunately, researchers simply are not yet proficient at measuring and conceptualizing that variation.

The third generalization concerning risk reduction among IV drug users is an apparently counterintuitive and synergistic relationship between "safer" injection programs and drug treatment to reduce or eliminate injection behavior. The common assumption that providing the means for safer injection will encourage drug use and undermine drug treatment is contradicted by the data collected to date. The Amsterdam syringe exchange program has been collecting data longer than any other program; its results clearly show that syringe exchange has not encouraged drug use. As noted earlier, the program was begun in 1984, during which 25,000 sterile needles and syringes were distributed. The number distributed rose to 700,000 in 1987; it is estimated that 750,000 sterile needles and syringes will be distributed in 1988. During this expansion period, there was no decrease in the number of persons entering either methadone maintenance or drug-free treatment programs. Moreover, there appeared to be no increase in the number of heroin users in the city, which remained constant at approximately 7,000-8,000. Approximately 25-30 percent of these users (or 1,750-2,400) report current injection behavior (van den Hoek et al., 1988b). During this period, the average age of IV drug users in the city increased, indicating that the group is an aging cohort with little influx of new users.

Two studies from Amsterdam indicate that the syringe exchange program might actually be associated with reductions in IV drug use rather than increases. In a study conducted by van den Hoek and colleagues (1988b), the number of subjects who were injecting on a daily basis decreased during the time the syringe exchanges increased. Buning and colleagues (1986, 1988) compared IV drug users in Amsterdam who participated in the syringe exchange program with IV drug users who did not participate. These researchers found higher rates of needle-sharing and an increased frequency of injection (both of which are associated with HIV infection) among drug users who did not use the exchange program.

Although syringe exchange programs in other locations abroad are still in the preliminary stages of development, none so far has reported any increase in drug use among clients. Similarly, there have been no reports from these programs of increases in the number of IV drug users in the early phases of drug-use careers. It appears that the programs provide needed services to IV drug users and facilitate their entry into drug treatment without being coercive (Hart et al., 1988; Ljungberg et al., 1988). Maintaining a nonjudgmental attitude toward participants and providing a range of risk-reducing options from which the IV drug user can choose may be two of the factors that are critical to the success of syringe exchange programs (Alldritt et al., 1988).

In the United States, there has been a similar complementarity between programs that provide the means for safer injection and drug treatment programs. As noted earlier, the first ex-addict outreach program in New Jersey evolved from one that taught sterilization methods into one with expanded treatment capacity (Jackson and Rotkiewicz, 1987; Jackson and Baxter, 1988). The outreach programs in New York and San Francisco that distribute bleach have had to develop referral-to-treatment programs and street counseling components to keep up with the demand for these services (Des Jarlais, 1987b).

Because of the well-known difficulty of ending drug use without any relapse (see Chapter 4), many treatment programs have seen the promotion of safer injection practices as complementary to their efforts to reduce or eliminate drug injection. A number of methadone programs in Amsterdam are also sites for the syringe exchange program (Buning et al., 1986; Buning, 1987b). At least one treatment program in San Francisco is a site for bleach distribution, and several programs in New York are teaching IV drug users how to use bleach to disinfect injection equipment (D. C. Des Jarlais, New York State Division of Substance Abuse Services, personal communication, August 1988).

Although there are as yet no data from long-term studies, current data suggest that safer injection programs and drug treatment can be complementary means to reduce the risk of HIV transmission among IV drug users. However, more research is needed to understand the mechanisms that link safer injection programs with the actual reduction of risk-associated behavior. To successfully implement innovative programs in this country, researchers and program operators must also understand how, in the absence of supporting data, people maintain beliefs about what does and does not encourage drug use.

Changes In Sexual Behavior

Although there is evidence of large-scale changes in injection behavior among IV drug users from many different geographic areas, there is little encouraging news with respect to the sexual transmission of HIV in this population. Early studies show that relatively few IV drug users are practicing safer sex (Friedman et al., 1987b; Watters, 1987a; van den Hoek et al., 1988b). Typically, for every two to three IV drug users who report changes in injection behavior, only one reports any change in sexual behavior. More recent studies support these findings. Table 3-2 lists the studies presented at the Fourth International AIDS Conference that were related to heterosexual transmission among IV drug users. All of them found less reduction of risk-associated sexual behaviors than of risk-associated injection behaviors: typically, only one quarter of those surveyed reported condom use. No one yet knows why sexual behaviors in this population resist change. There appear to be many potential reasons, including a realistic fear that introducing safer sex will lead to a break-up of the relationship (Casadonte et al., 1988) and difficulty in initiating a discussion of sexual topics (Mosely et al., 1988). As noted earlier, the typical sexual relationship of an IV drug user involves a male who injects drugs and a female who does not (Des Jarlais et al., 1984; Primm et al., 1988). The asymmetries of risk and power may thus contribute to difficulties in initiating safer sex practices.

TABLE 3-2

Studies of Sexual Behavior Change in IV Drug Users.

In a consideration of the reasons why IV drug users are not practicing safer sex, researchers should not neglect the reasons why the heterosexual population in general is not doing so. IV drug users are often treated by researchers as a population that is separate and discrete from the general public. Yet among the public are many subgroups that may share some beliefs, attitudes, and values with IV drug users. Among respondents to a recent national telephone survey who reported five or more sexual partners in the past year, more than 30 percent indicated that they had never purchased condoms during that time (Turner et al., in press). Intravenous drug users may simply be conforming to their community norms with regard to their sexual practices. In fact, deviation from those norms might call attention to their drug use and increase stigmatization. Moreover, it is important not to underestimate the potential for public confusion surrounding the dangers of heterosexual transmission and the negative impact of such confusion on behavioral change. Mixed messages have been given concerning the risks associated with heterosexual behavior.⁶

As noted earlier, there is an important exception to the lack of risk reduction in sexual behavior. Prostitutes have shown a willingness to use condoms with clients, although they report safer sexual practices less often in the context of personal relationships.

As discussed in Chapter 2, the determinants of patterns of sexual behavior are quite complex. It is unlikely that there is any single reason for the difficulties involved in facilitating change in the sexual behavior of most IV drug users. It will take careful research to elucidate these difficulties and their causes and to devise prevention strategies for helping individuals in this group change risk-associated behavior. Sudden breakthroughs in this area are not likely.

Toward Reducing Risk-Associated Behavior Among IV Drug Users

The problem of HIV infection among IV drug users and its transmission to their sexual partners and offspring requires both immediate action and long-term research. Immediate action is necessary because of the potential for the rapid spread of HIV among IV drug users within short periods. Although the current state of knowledge does not permit permanent or long-term solutions to drug-use problems and HIV infection in this population, enough is known now, on the basis of existing research and sound management techniques, to slow the spread of disease. In June 1988, the report issued by the IOM/NAS AIDS committee concluded that federal efforts to reduce HIV transmission among IV drug users were grossly inadequate. This committee concurs with that finding and recommends that the appropriate government authorities take immediate action to (1) provide drug treatment upon request for IV drug users throughout the country; and (2) sustain and expand current programs that provide for "safer injection" to reach all current IV drug users in the nation on a continuing basis and with appropriate research evaluation. From a public health perspective, it is unacceptable that persons who want to stop injecting drugs cannot receive immediate treatment. Furthermore, there is consensus among people who work in the area of drug use that treatment can produce a dramatic reduction in drug injection, even though relapse after treatment is a continuing problem (Des Jarlais, 1987a; Hubbard et al., 1988).

Preventing the spread of HIV infection requires more than additional treatment slots, however. Problems associated with drug-use relapse and with retaining individuals in treatment need to be solved; in addition, support is needed to maintain newly developed skills associated with positive treatment outcomes, such as job training, employment, and interpersonal skills. Preventing further infection also requires programs to alter those behaviors that are known to transmit HIV. Admittedly, there are insufficient data on how to provide the most effective AIDS prevention programs for those who inject drugs. Still, intervention programs cannot wait to implement findings that may take some time to generate.

As discussed in detail in Chapters 4 and 5, prevention programs should include planned variations of intervention strategies accompanied by sound evaluations to determine what is likely to be successful in preventing further infection and what is less likely to be helpful. Currently, however, there is no national system for monitoring ongoing prevention activities for IV drug users. The committee recommends that the appropriate government authorities take immediate action to establish data collection systems for monitoring present AIDS prevention efforts for IV drug users. At a minimum, a system is needed that provides data on the AIDS prevention services being offered throughout the country to IV drug users and their sexual partners, the rates of participation in these programs, and the characteristics of participants. Additional means must be used to reach those vulnerable members of the IV drug-using population who do not come into contact with the treatment system and to assess and serve their needs.

Reaching and serving these hard-to-reach IV drug users will require innovative methods and additional resources. Mobile vans and a cadre of outreach workers familiar with the IV drug culture, who can go into shooting galleries and other settings in which risky behaviors are occurring, have proven helpful in reaching individuals who have not been in touch with other services or agencies that deal with drug users. In short, services, whether education, information, or primary medical or social services, must be brought to IV drug users; it cannot be assumed that IV drug users will seek them out.

The committee finds that the severity of the AIDS epidemic does not permit a business-as-usual approach to the problems associated with IV drug use. All opportunities for halting the spread of HIV infection should be seized, intelligently and quickly.

Obviously, primary prevention of IV drug use would be an effective prevention strategy for HIV transmission associated with the injection of illicit drugs. Yet IV drug use is a long-standing problem in American society and has withstood many prevention efforts to date. All previous research indicates that, despite prevention and intervention efforts, a substantial number of persons will continue to inject drugs, at least over the short term. Some of these will be persons who refuse to accept treatment; others will be persons for whom current forms of treatment are not effective. Those already using drugs should be helped to modify risk-associated behaviors. If abstinence from drug use is not achievable, it should not detract from the pursuit of other goals related to stopping the spread of HIV.

A pluralistic, multitiered approach to HIV prevention is called for among IV drug users. Current studies indicate that safer injection programs are not associated with increases in IV drug use and do lead to large-scale risk reduction among IV drug users. The existing data on legal access to sterile injection equipment or the use of bleach as a disinfectant do not show which is the "best" type of safer injection program. Planned variations of these programs with appropriate evaluations are needed to learn more about designing and implementing more effective programs while simultaneously preventing further infection. These variations and the evaluation of safer injection programs should include both equipment sterilization efforts and needle exchange programs.

As detailed in Chapter 4, achieving and sustaining behavioral change is frequently difficult. The change that can reasonably be expected will not be perfect. For example, IV drug users may reduce the number of persons with whom they share injection equipment, but they may continue to share with a close personal friend or sexual partner. Indeed, as described later in this chapter, the use of the same injection equipment within a close relationship is sometimes not even thought of as "sharing" (Des Jarlais and Friedman, 1988). In addition, although IV drug users may exchange syringes "regularly" or decontaminate injection equipment "regularly," such "regular'' risk-reducing activity may not occur 100 percent Of the time. In the throes of narcotic withdrawal, almost all IV drug users report using whatever injection equipment is available (Des Jarlais et al., 1986a; Selwyn et al., 1987).

Given the high relapse rates of drug users after they leave drug treatment programs and the ineffectiveness of currently available treatment for some injectable drugs, the complete elimination of injection behavior is not a realistic goal. Change should be conceptualized as risk reduction rather than complete risk elimination. Moving toward a more moderate, more realistic set of goals will broaden the possible approaches to risk reduction programs; these efforts should include mechanisms to prevent relapse. The committee recommends that high priority be given to research that will lead to improved drug-use treatment, including studies of relapse prevention and of treatment for cocaine dependence. Applied research should include planned variation and evaluation of experimental programs.

Recent research indicates that HIV seroprevalence among IV drug users may have stabilized in several areas, including New York City (Brown et al., 1988; Des Jarlais, 1988), Stockholm (Bottiger et al., 1988), and Innsbruck (Fuchs et al., 1988). Although these developments are certainly encouraging, it is important to note that stabilization in a seroprevalence rate is also compatible with the introduction of new cases of HIV infection. Stabilization can result from the simultaneous loss of seropositive individuals (owing to migration, lack of participation in antibody testing programs after an initial positive test, and so forth) and the entry of seronegative persons into the local IV drug-using population. Modest rates of new infection could be sustained indefinitely and would not necessarily be detected by current survey strategies. The committee wishes to emphasize that the data indicating relative stabilization in HIV seroprevalence rates in these areas should not be construed to mean that the problems of HIV infection among IV drug users in those locales have been solved. Rather, these findings should be viewed as evidence of a capacity and willingness to change risk-associated behaviors in a population that has been characterized in the past as uncooperative and self-destructive.

Research Traditions

Research on illicit substance use has suffered from a disciplinary and topical balkanization, with scholars from various disciplines working independently, often with a discrete focus on a single substance. For example, biobehavioral research on IV drug use has had a twofold focus: explaining how illicit drugs can reinforce behavior and describing the mechanisms of tolerance that develop after repeated administration of certain drugs. Psychiatric and psychological research, on the other hand, has tended to define substance use as a form of mental illness. This tradition has sought to identify the precursors of illicit drug use and to assess the effectiveness of different types of psychotherapy for treatment. Sociological and anthropological research in the area has focused on drug use as a form of social behavior and thus has explored drug-user subcultures—their norms, beliefs, and values. This research has also examined the relationships between drug use and other deviant behavior, particularly criminal activity, and the relationships among race, social class, and IV drug use. Research into the causes and cures of drug use has also been complicated by competing views of drug use as a medical (and public health) or moral (and criminal law) problem (Drew, 1986).

Most of what is currently known about drug users comes from users who have been involved in treatment programs and users who have come into contact with law enforcement agencies (Ginzburg, 1984). Little is known about those users who are not in touch with these systems. (Some of the problems of using such circumscribed data soon become apparent when this information indicates that ethnic and racial minorities are overrepresented in public treatment programs [Ginzburg et al., 1987] and there are few data on individuals who seek treatment in private health care settings.) In addition, data have been collected primarily to satisfy policy needs related to treatment and criminal justice, uses that determine what kinds of data are collected. Individuals who make plans for treatment programs need to know how many people will require their services and how to make their programs culturally sensitive to the populations they serve; criminal justice agencies require information about the role of drugs in crime. The data that serve these purposes are not necessarily adequate or appropriate for infectious disease containment efforts.

Researchers are only now beginning to collect data on the behaviors associated with HIV transmission in the IV drug-using population. The Heroin Lifestyle Study (Hanson et al., 1985), which was conducted in the early 1980s in the inner cities of Chicago, New York, Philadelphia, and Washington, D.C., cast some of the first rays of light on IV drug-use behaviors that are relevant to AIDS. What emerges from these studies is a more detailed description of behaviors that show variability by race, ethnic group, gender, age, and geographic location.⁷ To understand more about this variability and gather more subgroup-specific information, field workers who are often ex-addicts and ex-offenders are being recruited to locate active IV drug users in shooting galleries, after-hours clubs, and the like. In these attempts, they gather data on daily drug-use and related behaviors, take life histories, and make observations.

Despite these promising beginnings, however, there remain certain logistical hurdles and methodological problems that need to be cleared away before we can move more effectively toward the goal of reducing risk-associated behavior among IV drug users.

Tied as it has been to policy needs, research on drug use in the past suffered the vicissitudes of shifting policies and resource availability. For example, the Client-Oriented Data Acquisition Process (CODAP)⁸ collected demographic data and drug-use histories on all individuals entering federally and state-funded drug treatment programs. In the early 1980s, however, what had previously been direct federal support for this and other drug-related programs was superseded by a block grant program that shifted control from federal agencies to the states. When the total funds allocated to these efforts were cut, many states, exercising their discretionary powers over the design and management of drug programs, unfortunately chose not to continue collecting CODAP data.

Still, significant research has been conducted and data of variable quality have been collected, but topics remain that are either underexplored or that have not been investigated at all. Most studies on IV drug use have investigated the injection of heroin; much less is known about the injection of cocaine or other drugs. In addition, methodological limitations persist. The methodological problems are as diverse as the population to which drug researchers wish to apply methodologies. Drug users do not necessarily cooperate as research subjects by restricting their behavior to forms that can be studied using simple questionnaires. For example, single-substance drug use lends itself relatively easily to research design; the polydrug use that a significant portion of IV drug users actually report is much more difficult to measure (B. D. Johnson et al., 1985). To investigate these topics properly, old methodologies must be improved and new ones devised. The next section discusses some of the challenges inherent in these tasks.

Investigating Risk-Associated Drug Behaviors

Researchers use two basic methods to understand the nature of drug use and the extent of consumption patterns: (1) statistical surveys of defined populations and (2) ethnographic studies. Each approach focuses on quite different populations (the overlap of which is unknown) and uses very different methodologies. Analyses of the drug-using population also rely on self-reported data and on indirect indicator data, which are provided by institutional sources (e.g., treatment programs, emergency rooms, medical examiners, the criminal justice system). Some of the ways in which these approaches can be used in research on IV drug use are discussed below.

Toward Better Quality Data

The need for better information about IV drug users has prompted the committee to recommend that high priority be given to studies of this population. Little is known about variations in the injection patterns of adolescents, minorities, women, and other IV drug users who do not come into contact with organizations and agencies that serve the drug-using population. Studies are also needed of those IV drug users who are not being captured by current sampling strategies. These "invisible" drug users are apt to include individuals in the mainstream of society (i.e., from upper and middle socioeconomic classes) who are more likely to seek treatment in private health care facilities.

The status of IV drug users as members of the heroin community is often secret. These users may or may not be identified on the street as addicts, depending on their means of obtaining the drug and the stage of their drug-use careers. Their drug use may be hidden even from family and friends. The committee recommends that high priority be given to studies of IV drug users who are not in contact with health care, drug-use treatment, or criminal justice systems.

Reaching the relevant groups to collect data and deliver intervention programs and services will not be easy. The successful recruitment of IV drug users into drug treatment and intervention programs and into research protocols, and their subsequent retention in such efforts, will require careful management of those procedures and practices that could identify participants. Intravenous drug users often view the identifiers required in some research as an invasion of privacy and a means of uncovering issues and behaviors that they do not want uncovered. Yet these same identification practices can improve the quality and richness of data and facilitate the evaluation of programs. A careful balance must be struck between serving the need to collect useful data and respecting the sensitivities of study respondents.

Also needed are methodological studies of how to obtain better self-reported information and how to determine when a particular subject is not providing valid data. It is critical to understand under what conditions IV drug users are more or less likely to disclose information and to remember past events accurately, particularly those events that may involve complex and variable patterns of behavior such as needle-sharing. Techniques that have been tried in other areas (e.g., varying the setting of the interview or asking the respondent to record sensitive information without being observed by the interviewer) deserve further investigation. The committee recommends that high priority be given to methodological studies to determine ways of improving the quality of self-reports of sexual and drug-use behavior. Conducting such studies, however, will require a long-term commitment to research on illicit drug use; the benefits of methodological research, including a better understanding of how to maximize the validity of self-reported data from persons who use illicit drugs, will be evident as the findings from such research are incorporated into future studies.

Sampling IV drug users is difficult, both theoretically and operationally. Typical statistical sampling procedures may not yield useful estimates, and even procedures that have been designed to sample rare and elusive populations (Sudman et al., 1988) are problematic. Using such techniques as geographically clustered samples and network samples can help inform the estimation process. Regardless of the method or combination of methods used, the estimation process will continue to rest more on judgment than on formal statistical inference.

Prevalence Of IV Drug Use

Estimates of the number of IV drug users and the rates of seroprevalence among them are an essential feature of overall attempts to gauge the spread of AIDS, to target intervention programs, and to plan for the health care resources that are likely to be needed in the future. Inaccurate estimates of the nature and scope of the IV drug-use problem may hinder the formulation of appropriately targeted AIDS prevention policies. Moreover, inadequate data can stymie efforts to refine understanding of the relative degree of peril associated with the behaviors that are known to transmit HIV.

Currently, the accurate estimation of the prevalence of IV drug use is hindered by (1) the lack of a sound conceptual model of the dynamic nature of IV drug use, (2) the lack of appropriate statistical models, and (3) the limitations of existing data and data collection systems. Any attempt to improve the estimation process will require major efforts in each of these areas. Without such efforts, the basic assumptions underlying HIV seroprevalence estimates and other rates that require a sound denominator will continue to be questioned.

Estimates of the total number of IV drug users were published in the November 1987 report prepared by the Public Health Service for the White House Domestic Policy Council and in a special supplement to CDC's Morbidity and Mortality Weekly Report (CDC, 1987a,b). One of the background papers commissioned by the committee (see Spencer, in this volume) contains a critique of the estimates generated in that report to illustrate the lack of data and models for assessing the extent of IV drug use in the United States. The deconstruction of current estimates (i.e., breaking down the totals into the components on which they are based) indicates that these estimates may be subject to substantial error. One possible source of error is the lack of agreement among those providing data on who should be counted in the ranks of the IV drug-using population.

Definition Of An IV Drug User

A basic problem in constructing estimates of drug use is the difficulty of defining the term IV drug user. The types and combination of drugs injected and the frequency of needle use vary considerably among users, as do individual drug-use "careers." Hard-core or addicted users may inject many times daily; other IV drug users may inject less frequently and may never become addicted (Gerstein, 1976; Zinberg, 1984; Hanson et al., 1985). Indeed, during their drug-use careers, individuals may move through phases of regular and intermittent use (Simpson et al., 1986). However, all phases that involve needle-sharing carry some level of risk (albeit a variable one) of contracting HIV infection. Furthermore, those ex-users who are now asymptomatic may already be infected from prior needle-sharing.

When using multiple data sources to estimate the total number of IV drug users, it is important to keep the drug user definition constant across all sources. The level of precision of this definition for any given study will depend on the study's purpose. To study the transmission of HIV infection, for example, researchers will need to estimate seroprevalence for IV drug users classified by frequency of injection, how long they have been injecting, whether they share needles and with whom, as well as other relevant dimensions of drug use.

In its 1987 report, CDC (1987a) distinguished between two types of IV drug users: regular users, who inject at least once a week, and less frequent or occasional users, who inject less often than regular users but who have used drugs more than just once or twice. Two sets of national estimates were produced for each type of IV drug user: the original Public Health Service estimates for 1986 and revised estimates for 1987 (see Table 3-3).

TABLE 3-3

Estimated Number of IV Drug Users and Their HIV Status.

To assess the accuracy of these estimates, it is necessary to know the population definitions that were used in estimating the total number of each type of IV drug user and the seroprevalence rates. How different are the operational definitions? How accurate are the estimates for the populations as operationally defined?

Prevalence Of AIDS And HIV Infection Among IV Drug Users

Approximately one quarter of all AIDS cases diagnosed in this country among adults and adolescents is related to IV drug use (Schuster, 1988). However, because of the very strict definition of AIDS that has been established for surveillance purposes, it is thought that the number of reported cases underestimates the size of the problem. A review of death certificates in 1985 found reporting to be 90 percent complete. Still, Hardy and coworkers (1987) have suggested that an additional 13 percent of deaths among IV drug users were related to HIV but did not meet the CDC criteria for AIDS. The number of non-AIDS deaths among IV drug users in New York City increased from 257 in 1978 to 1,607 in 1985 (Des Jarlais et al., 1988b). This increase is presumed to reflect fatal consequences of HIV infection that did not meet the CDC surveillance definition for AIDS, including infections from nonopportunistic pathogens (see Table 3-4). Other factors, such as better record-keeping or better surveillance, can also result in increases in the number of reported deaths; however, one study of narcotic-related deaths in New York (Stoneburner et al., 1988) ruled out improved recognition and reporting in explaining increased mortality.

TABLE 3-4

Selected Causes of Non-AIDS Deaths Among New York City IV Drug Users in 1981 and 1985.

Unfortunately, less is known about the rates of HIV infection among IV drug users than is known about the prevalence of AIDS. Much of the data on HIV infection in this group has been collected from small samples of convenience recruited from methadone maintenance programs, drug-free treatment programs, detoxification programs, prisons, and the street. With such limited data, it is not possible to know the prevalence of HIV infection among IV drug users in the United States at this time. What researchers are beginning to suspect, however, is that the number of AIDS cases may not accurately reflect the disease burden of this population. What is known is that there is great variability in rates of infection across the country (Table 3-5). Geographic variation in the number of AIDS cases indicates that there are still important opportunities to prevent the further spread of the disease. The following paragraphs discuss what is known about HIV infection and describe the patterns that have been seen to date.

TABLE 3-5

Percentage of All Reported AIDS Cases Among IV Drug Users in the United States.

Reviews of HIV seroprevalence studies of IV drug users show persistent associations of seroprevalence rates with geography and ethnicity (CDC, 1987a; Des Jarlais and Friedman, 1987b; Curran, 1988; Hahn et al., 1988). In the United States, there are wide variations in HIV seroprevalence by region of the country. As shown in Table 3-6, for individuals reporting IV drug use, the rates of HIV infection are highest in the New York City area (typically, 50 percent or higher); intermediate (15-35 percent) in other urban areas (e.g., Baltimore, Hartford, and San Francisco); and very low (5 percent or lower) in some western cities (e.g., Los Angeles).

TABLE 3-6

Seroprevalence Among IV Drug Users Tested in Various Settings in Selected U.S. Cities and States.

Several factors contribute to the geographic variability of HIV seroprevalence rates among IV drug users in the United States. First, most IV drug users do not appear to travel extensively. In addition to limited economic resources, the need for a constant supply of drugs probably reduces their mobility, although they appear to travel some, especially to locations where friends can help them obtain drugs. Other IV drug users—for example, prostitutes or those who sell drugs—may be induced to travel by their ability to earn money in new cities. Data on the life-styles of IV drug users include little information on physical mobility. Clearly, additional research in this area will be needed to target prevention strategies and to model the future course of the AIDS epidemic.

The second factor influencing the great geographic variation in HIV seroprevalence is the potential for the rapid transmission of infection within a particular locale. As is seen with other infectious diseases, a self-sustaining epidemic occurs when one infected individual produces new infection in more than one other person (see Chapter 1). Using blood samples collected and stored from previous investigations, researchers have reported increases (from approximately 10-50 percent or greater) in seroprevalence over a period of 3-4 years in New York (D. M. Novick et al., 1986; L. F. Novick et al., 1988); Edinburgh, Scotland (Robertson et al., 1986); and Milan, Italy (Angarano et al., 1985; Moss, 1987). The committee wishes to point out, however, that these rapid increases occurred prior to widespread awareness of AIDS. Given current knowledge of HIV transmission and of behavioral change associated with prevention activities, the rapid spread of HIV infection among IV drug users should not be seen as inevitable.

Geographic variation in rates of infection may also reflect the disproportionate burden of disease borne by racial and ethnic minority groups. Chaisson and coworkers (1987b) found HIV infection among IV drug users in San Francisco to be significantly more prevalent among blacks and Hispanics than among whites. Weiss and colleagues (1985) reported similar findings in New Jersey. As of November 14, 1988, of all reported AIDS cases, 26 percent were diagnosed among blacks and 15 percent were diagnosed among Hispanics (CDC, 1988). Of the cases attributed to IV drug use, blacks accounted for 50 percent and Hispanics accounted for 30 percent.¹⁸

Although consistently higher seroprevalence rates have been found among minority IV drug users, more complete interpretations of the data raise questions about factors that may differentially predispose minorities to HIV infection. In some studies (e.g., Marmor et al., 1987b), racial and ethnic differences do not retain statistical significance after controlling for drug use and needle-sharing. However, in the study of IV drug users from San Francisco, both blacks and Latinos were found to have a greater prevalence of HIV infection than whites, a finding that persisted after adjusting for reported needle-sharing (Chaisson et al., 1987b). The reasons for these differences are not yet understood. There may be behavioral differences in IV drug-use and needle-sharing behaviors across ethnic groups that are actually more accurately measured by questions on ethnicity than by questions on the behaviors themselves. Clearly, the amount of error in measuring ethnicity is likely to be much less than the error in measuring complex behavior over long periods of time. In other studies (e.g., Schoenbaum et al., 1986), racial and ethnic differences may be due to the recruitment of subjects from different areas within a single city, thus reflecting residential segregation and perhaps multiple epidemics of HIV within one city.

The frequency of ethnic differences in seroprevalence rates clearly indicates a need for additional research to explain these differences and the careful development of prevention strategies to reduce the chances of becoming infected, as well as the stigmatization and scapegoating of subpopulations. The committee recommends that high priority be given to research on the estimation of the current number of IV drug users in the United States and of seroprevalence rates among different groups of IV drug users.