The burden of chronic disease carried by racial and ethnic minorities affects the well-being of the general public through increasing medical expenses, years of potential life lost, and loss of revenue for medical and social service programmes . Although health disparities among racial and ethnic minority groups are receiving increased attention, efforts to develop and implement prevention and intervention programmes aimed at reducing these disparities are still needed .
It may be useful to view health disparities between racial/ethnic minorities and non-Hispanic whites in at least four contexts: those differences related to healthcare access (e.g. health insurance coverage); those differences related to medical outcomes (e.g. variations in medical procedures); those differences related to the incidence and prevalence of chronic or communicable diseases (e.g. diabetes, HIV); and those differences related to mortality rates (e.g. specific cancers, heart disease). It is the third context that this article will consider.
Studies have demonstrated the existence and persistence of specific racial/ethnic disparities in the incidence and prevalence of heart disease, diabetes mellitus, and certain types of cancers [3,4]. What may be less well known are the disparities related to common blood-borne viral pathogens such as hepatitis B virus (HBV) and hepatitis C virus (HCV), which may contribute to the observed higher mortality rates from liver disease and cirrhosis found among African-American and Hispanic individuals in comparison with non-Hispanic whites .
African-American and Hispanic individuals, in general, have higher prevalence rates of hepatitis B and hepatitis C than non-Hispanic whites [5,6]. However, African-American and Hispanic injection drug users (IDU) are at an increased risk of acquiring and transmitting HIV, HBV, and HCV . Moreover, several studies have noted the high co-occurrence of HIV and HBV, and HIV and HCV among IDU, as well as tri-infections of HIV, HBV, and HCV [7–14].
Given the increased likelihood of HIV, HCV, and HBV transmission and acquisition via drug injection, it is clearly appropriate to focus on early healthcare access and clinical treatment for those IDU who are mono-infected, co-infected, or tri-infected. Behavioral interventions for those who are HIV, HCV, or HBV positive are also needed to reduce the high probability of transmission to others. Because injection drug use is so highly associated with the transmission of HCV, HBV, and HIV, and unprotected sex with an infected IDU is the principal mode of transmission of HIV and HBV, substance abuse treatment in the form of methadone maintenance or bupenorphine may hold promise in halting the spread of these viruses among IDU and their sexual partners [15,16].
Racial/ethnic disparities in HIV/AIDS
Surveillance data collected by the Centers for Disease Control and Prevention clearly shows that African-American and Hispanic individuals are disproportionately represented in the HIV/AIDS statistics in comparison with their representation in the general United States population, accounting for almost 70% of the reported AIDS cases in 2003 . For example, although African-American individuals represent approximately 12% of the nation's population, in 2003 they represented half of all AIDS cases. Hispanic individuals represent approximately 14% of the US population, but in 2003 accounted for 20% of the total AIDS cases. Conversely, although non-Hispanic whites comprise 69% of the total US population, they represented 31% of AIDS cases reported in 2003. Moreover, African-American and Hispanic women accounted for 78% of all female AIDS cases, and 82% of all pediatric AIDS cases .
As shown in Table 1, in 2003 AIDS rates were very different for African-American and Hispanic individuals in comparison with non-Hispanic whites. Among adult/adolescent men, African Americans had almost 10 times the rate of non-Hispanic whites, and almost twice the rate of Hispanic individuals. In addition, Hispanic individuals had almost three times the rate of non-Hispanic whites. Among adult/adolescent women, African Americans had 25 times the rate of non-Hispanic whites, and four times the rate of Hispanics. Hispanic women had AIDS rates six times higher than non-Hispanic whites. Similarly, for children less than 13 years of age, African Americans have 10 times the rate of non-Hispanic whites and three times the rate of Hispanic individuals, whereas Hispanic individuals have three times the rate of non-Hispanic whites.
The impact of drug injection as a transmission mode on African Americans, Hispanics, and non-Hispanic whites is shown in Table 2. As seen, the proportion of adult/adolescent AIDS cases caused by injection drug use is approximately three times higher in African-American and Hispanic men in comparison with non-Hispanic white men. Conversely, non-Hispanic white women have a slightly higher proportion of AIDS cases related to IDU than African-American and Hispanic women.
Reported cases of HIV infection (not AIDS) caused by injection drug use are also shown in Table 2. African-American and Hispanic men have almost twice the rate of HIV infection of non-Hispanic white men, but interestingly, non-Hispanic white women have rates almost twice as high as African-American and Hispanic women.
The higher rates of HIV infection and AIDS cases reported by the Centers for Disease Control and Prevention for African-American and Hispanic adolescents and adults varies by sex and transmission category. For the transmission category of injection drug use, non-Hispanic white women have higher rates than African-American and Hispanic women, but among men this situation is reversed. Certainly, more research needs to be done to examine why this may be the case. What is clear, however, is that the United States will continue to experience racial and ethnic disparities related to HIV and AIDS over the next decade unless prevention and intervention programmes are implemented and targeted to high-risk groups in African-American and Hispanic communities.
Disparities in common blood-borne pathogens: hepatitis C virus and hepatitis B virus
In general, the prevalence of HCV is higher among African-American and Hispanic individuals, especially Mexican Americans, than non-Hispanic whites . National surveys (e.g. NHANES III) have documented HCV prevalence rates for African-American and Hispanic individuals by age . For African-American individuals the prevalence rates ranged from approximately 1.8% for ages 20–29 years to approximately 6.5% for ages 30–49 years, which was a twofold difference in comparison with non-Hispanic whites. For Mexican-American individuals, the only Hispanic subgroup included in the study, prevalence rates increased from approximately 2% in the 20–29 year age group to approximately 6% for those between 50 and 59 years, which was six times the rate among non-Hispanic whites .
As noted by Diaz et al.  in 2001, HCV rates among IDU range between 60 and 90%, with great geographical variability . Several studies have also shown that the duration of drug injection is one of the strongest predictors of HCV infection [18–20]. For example, after 3 years of injecting, as many as 30% of IDU become infected with HCV, and after 5 years more than 50% can be infected . Studies have also shown that the sharing of injection paraphernalia such as cookers or cottons is also highly predictive of HCV infection [18,21,22].
Unequivocal estimates of the incidence and prevalence of injection drug use in the USA are difficult to obtain. Methodological differences in study design, sample representativeness, and validity and reliability of self-reported drug use have all hampered attempts to generalize findings. A well accepted set of studies in the field of substance abuse ‘The Monitoring the Future Study’ provided lifetime estimates of heroin use ranging from 1.2 to 3.1%, depending on the age range. Lifetime rates of heroin use with a needle are lower, with approximately 1% ‘ever’ having used heroin with a needle . Some evidence suggests that these rates are much higher among Hispanic and African-American individuals . Given the body of research showing that injection drug use is the most effective method of HCV transmission, it should come as no surprise that the burden of this disease weighs heavily on both African-American and Hispanic IDU.
HBV incidence is highest among African Americans, followed by Hispanics and non-Hispanic whites, and highest among individuals aged 25–39 years . Similar to HCV, several studies have demonstrated a significant correlation between HBV prevalence and the duration of drug injection; within 5 years of injecting between 50 and 70% of IDU become infected with HBV [7,10,11,13,14].
On the basis of what is known regarding the use and sharing of injection paraphernalia among IDU , it is evident that IDU who share are at an increased risk of acquiring HBV through either sexual or syringe-mediated transmission routes. Levine et al.  reviewed several studies on the prevalence of HBV among IDU, and provided a weighted average prevalence rate of 74.2%, with rates ranging from 50.9 to 89.6%. Chamot et al.  reported that the annual incidence of HBV among IDU ranged from 0.9 cases per 1000 IDU to 4.8 cases per 1000 IDU. Lopez-Zetina et al.  found that approximately 80% of street-recruited IDU tested positive for antibodies to HBV. Several studies have also documented racial/ethnic differences among IDU and HBV prevalence [10,13,14]. Such studies showed that Hispanic and African-American IDU have higher prevalence rates of HBV than non-Hispanic white IDU.
As noted previously, it has been presumed that African-American and Hispanic individuals have higher rates of injection drug use than non-Hispanic whites . Data also showed that African-American and Hispanic individuals, in general, have higher incidence and prevalence rates of HBV and HCV [5,6]. It makes intuitive sense, then, that there would be higher rates of HBV and HCV among African American and Hispanic IDU who are at an increased risk of the acquisition and transmission of these viruses. Some research has supported this speculation [12–14], but much more research needs to be conducted to examine the relative risk of HBV and HCV infection among African-American and Hispanic IDU.
Prevalence of HIV and hepatitis C and B virus risk behaviors among African-American and Hispanic injection drug users
Much is known about the major routes of HIV, HCV, and HBV transmission among IDU . For the majority of IDU, these risk factors can be divided into two major transmission risks: injection-related or syringe-mediated, and sexual. Common risks associated with injection-related or syringe-mediated transmission include the duration and frequency of injection, pooled drug purchases, multi-person reuse of syringes without bleaching, and ‘indirect’ sharing of injection paraphernalia such as the cottons, cookers, and rinse water, or using drug dispersal methods such as front-loading or back-loading. Sexual transmission risks include unprotected sex with an infected individual, concurrent multiple sexual partners, exchanging sex for money or drugs, and having a history of sexually transmitted infections. Beyond these two transmission risk categories, other risk behaviors include incarceration, tattooing and body piercing, sharing of contaminated personal care items, and blood transfusions before 1993.
Estrada et al.  examined the prevalence of several of these risk behaviors among African-American and Hispanic IDU using a large, national dataset.
The study documented that Hispanic IDU, specifically Mexican-American and Puerto Rican IDU, injected more frequently, shared drug paraphernalia more often, and disinfected with bleach less often than African-American IDU. As seen in Table 3, statistically significant results emerged suggesting differential risks. Puerto Rican IDU had significantly higher prevalence rates associated with the frequency of injection and intensity of injection (times/day) than Mexican-American or African-American IDU. Mexican-American IDU had significantly higher prevalence rates associated with sharing injection paraphernalia such as the number of times they knowingly used used works. Puerto Rican and Mexican-American IDU reported significantly higher rates of using used supplies that had been used by others. It would appear that much more sharing of injection paraphernalia occurs among the two Hispanic subgroups of IDU, and in comparison, African-American IDU have much lower rates of injection frequency and sharing of injection paraphernalia. Although not statistically significant African-American IDU used bleach 49% of the time, Puerto Rican IDU used bleach 46% of the time, and Mexican-American IDU used bleach only 35% of the time.
Epidemiological paradox or differential transmission?
When one examines the HIV/AIDS incidence and prevalence data one is struck by the profound racial and ethnic differences, not only between African Americans, Hispanics and non-Hispanic whites, but also between African-American and Hispanic individuals. Why should this be the case if both groups are similarly socioeconomically disadvantaged? Previous research examining health disparities have suggested an apparent ‘epidemiological paradox’ between African-American and Mexican-American individuals with regard to certain cancers, heart disease, and stroke . Most researchers in this area speculate that there must be some type of ‘protective’ factor operating among Mexican-American individuals that mitigates their risks, which are not operant in African-American individuals. But what about other Hispanic subgroups such as Puerto Ricans? Extant research would suggest that Puerto Ricans have poorer health outcomes than Mexican-American individuals, even though their access to healthcare is greater than that of the latter group [4,29]. But what is the relationship with the acquisition and transmission of blood-borne pathogens? Are there real differences in relative risk among African-American, Mexican-American, and Puerto Rican IDU in relation to the acquisition and transmission of HIV, HCV and HBV? An examination of risk factors conducive to the transmission and acquisition of these blood-borne pathogens shows that Hispanic IDU may be at higher risk than African-American IDU in relation to syringe-mediated risk behaviors. However, more research needs to be done examining the differential risks in sexual transmission of these blood-borne pathogens. Estrada et al.  have shown that Puerto Rican IDU tend to inject more frequently, and tend to inject more common intravenous drugs (e.g. heroin, speedball) than Mexican-American or African-American individuals. These findings suggest the possibility that African-American IDU who are seropositive for HIV, HBV, or HCV are transmitting these infections to others primarily through unprotected sex, and seropositive Mexican-American and Puerto Rican IDU are transmitting these infections to others primarily through syringe-mediated risk behaviors.
It is also possible that the observed differences are based on social network composition that may be either more ‘closed’ or ‘open’ depending on the characteristics of the network members. Nevertheless, there are still many unanswered questions: Is the reservoir of HIV infection larger among African-American IDU than Mexican-American or Puerto Rican IDU? Is the reservoir of HBV and HCV infection larger among Mexican-American and Puerto Rican IDU than African-American IDU? Given the higher HCV and HBV prevalence and incidence found among Mexican-American and other Hispanic subgroups such as Puerto Ricans in relation to non-Hispanic whites [5,6] one might conclude that the transmission of these blood-borne pathogens may be facilitated more by the syringe-mediated risk behaviors of Hispanic IDU, and to a lesser extent by their sexual risk behaviors.
In conclusion, several caveats are in order regarding the studies cited in this review. Many differ in time, place, research design, sample selection, and thus generalizability. Some of the studies used complex multistage sampling designs, whereas others used convenience sampling methods. There is also the issue of self-report related to drug use and hepatitis [30,31]. Taken together, however, most of the studies reviewed agree that the prevalence rates of HIV, AIDS, HBV, and HCV are higher among African-American and Hispanic IDU than non-Hispanic white IDU; and risk factors conducive to the spread of these blood-borne pathogens are highly prevalent among Hispanic IDU, especially Mexican-American and Puerto Rican IDU, in comparison with African-American IDU.
The more profound implications of the current situation are that future generations of African-American and Hispanic children will continue to succumb to these common blood-borne pathogens, and the disparities seen currently will not be eliminated. Nothing short of a comprehensive approach is necessary to eliminate these disparities . However, it is not altogether clear that all three blood-borne pathogens (HIV, HCV and HBV) can be reduced by effective behavioral and structural interventions [32–35]. Some studies still show high-risk behaviors conducive to the transmission of these blood-borne pathogens among syringe exchange participants. Nonetheless, syringe exchange programmes can facilitate access to health services, and early intervention in the injection drug use career can alter HCV and HBV incidence and prevalence [35,36]. There is a vaccine for HBV. There are therapeutic treatments for HIV and HCV, but there is no vaccine. Linkages between sexually transmitted infection screening and HIV, HBV, and HCV case identification have been proposed by public health professionals . The correctional system can also play a major role in curtailing the observed higher rates of blood-borne pathogens among African-American and Hispanic IDU . Mandatory serology testing in correctional settings should be advocated, albeit with full protection for those tested. Prevention, intervention, and treatment can then be implemented, with appropriate aftercare upon release to the community. Recent estimates indicate that between 12 and 39% of those infected with HBV or HCV were released from correctional settings in the previous year . Clearly, these individuals can infect others if not appropriately treated.
Behavioral and cognitive interventions that target those who are positive (HIV, HBV, or HCV) are also required. Recent initiatives by the US federal government have specifically sought to curtail the HIV/AIDS epidemic by focusing on this population of positive individuals. Once HIV-positive individuals are identified and brought into medical care they can also be screened for HBV and HCV. In addition, positive individuals can be counseled to maintain risk-free behaviors that contribute to the transmission of these blood-borne pathogens.
Certainly, these recommendations are not without their problems, and would face formidable challenges to implementation. Nevertheless, the public's health continues to be at risk, and the increased burden of disease on African-American and Hispanic individuals will persist if comprehensive approaches are not envisioned and implemented in the near future.
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