HIV-related structural factors are defined as barriers to, or facilitators of, an individual's HIV-prevention behaviors. They directly or indirectly affect an individual's ability to avoid exposure to HIV. These factors have different names in the literature - environmental, structural, societal, super-structural, policy, contextual and others - often reflecting the disciplines and experiences of the writers. The broad term 'structural' is used in this paper, with the assumption that its meaning will become clearer and more differentiated as work in this area progresses.
International research demonstrates the potential of structural interventions for reducing HIV risk . Specific examples include: the 80% increase in condom use among commercial sex workers following a policy requiring the use of condoms in brothels in Thailand ; a 45% difference in HIV prevalence among intravenous drug users in two cities in Scotland, attributed to differing enforcement of paraphernalia laws ; a 10% increase in requests for HIV tests by pregnant women following provision of testing in south-eastern France ; and increases in reports of condom use between steady partners by up to 24% and between casual partners by up to 48% following implementation of a comprehensive national prevention policy in Switzerland . Additional studies have linked structural factors and HIV prevention in the United States [6-13], and review articles have assessed collections of studies and confirmed the importance of structures to HIV risk [1,14-19]. Studies addressing disease prevention and health promotion in other areas of public health, including infectious diseases, food-borne illnesses, environmental health, chronic disease, infant mortality, and injury and violence prevention corroborate the importance of structures to prevention .
Increasingly, writers envision changes that would remove barriers to or erect facilitators for effective prevention [17,19,21-38], and that would address HIV by increasing human rights [38-40]. The purpose of this paper is to help support and direct research that will characterize existing structural facilitators and barriers to prevention, and evaluate the impact of structural changes on HIV risk behaviors and infection.
Research on structural factors and interventions
Research on HIV prevention needs to target multiple levels, including individuals and the environments that influence their behavior. Biomedical and behavioral research have addressed HIV primarily at the level of individuals, providing treatment and prevention for HIV and AIDS, and behavioral interventions such as education, counseling and testing, small group counseling and skills development, and information and prevention motivation provided by peers in a community context. These behavioral approaches have been summarized by various reviewers [22,41-48]. Although there are relatively few rigorous experimental studies of behavioral interventions to prevent HIV [22,46], there is sufficient evidence to support the replication and dissemination of individually focused strategies . In addition to these individual-level studies, researchers are called to examine family-focused strategies [10,50-52], community-level interventions [16,53-55], inequality among social and demographic groups [34-36,40,56], and interventions to build prevention capacity and sustainability in affected communities [10,57].
Research that demonstrates the relationship between structural factors and HIV is rare, particularly in the United States. However, several published studies exemplify how structural factors may facilitate or inhibit HIV prevention. Albert et al.  studied a structurally mandated intervention targeting female brothel workers and their clients. In 1988, the state of Nevada passed a law requiring condom use in legal brothels. This law allowed women working in the brothels to insist on condom use with clients, and to devise strategies to serve clients who were reluctant to use condoms. It also led brothel owners to install safeguards such as buzzers in rooms or security personnel to help women deal with uncooperative clients. Because income for the women was dependent on keeping the brothels open, there was economic pressure for them to comply with the law. Very few clients (2.7%) refused to use condoms, and there was no incidence of HIV and negligible incidence of sexually transmitted diseases among the brothel workers after the condom law was passed.
Two studies provide examples of interventions that facilitated prevention behaviors by instituting policies related to HIV testing. In 1985, the Department of Public Health in San Francisco began contacting the partners of index cases and offering them HIV information, counseling and testing . Only 12% of the partners who were contacted refused to be interviewed. Of those interviewed, all elected some form of follow-up, and 58% elected to be tested for HIV. The health department policy increased the likelihood that exposed persons would know of their risk, and seek follow-up services and testing. At about the same time, in 1986, 25 Oregon counties initiated anonymous HIV counseling and testing . During pretest counseling, clients could choose confidential or anonymous testing. Over three times as many clients were tested during the 3 months following the new policy compared with the preceding 3 months. Of those tested after the new policy, 29% of clients overall, and 49% of men who have sex with men, reported that they would not have accepted testing if their identities were confidential but not anonymous. The new policy removed a significant barrier to an important preventive behavior.
Cost may be a structural barrier to the acquisition and use of condoms. Researchers interviewed patrons of local stores in a community in Louisiana, and asked how they obtained condoms and whether they used them during their last sexual encounter . Surveys were conducted while condoms were freely available in these businesses, and after a small (25 cent) charge was imposed. The researchers found that individuals who reported picking up free condoms were significantly more likely to report using condoms during their last sexual encounter than those who reported not picking up free condoms. Persons with two or more sex partners were significantly more likely to report using condoms when they were free than when they had to pay the low price. The authors concluded that cost is a barrier to condom use, and that free condoms should be available to persons at risk for HIV.
Another study described the impact on HIV-related behaviors of a structurally imposed barrier to prevention. Researchers assessed the impact of the closure of a needle-exchange program for intravenous drug users in a town in Connecticut. Before closure, 14% of interviewed intravenous drug users reported unsafe sources for syringes and 16% reported sharing a syringe in the past 30 days. After closure of the exchange, those reporting unsafe sources increased to 51% and those reporting sharing a syringe increased to 34%. After closure, the rate of reusing syringes doubled among those surveyed [7,13].
Educational interventions, such as teaching people about HIV or how to be safe from infection, are not structural per se. However, policies supporting the provision of education or information may be structural. Examples might be hospital policies to teach universal precautions to staff or to provide information to mothers on prevention of perinatal transmission, or a policy adopted by a nonprofit organization to inform local legislators about the impact of discrimination and stigmatization on HIV risk among minorities or men who have sex with men. Researchers in Seattle instituted an organizational system to train and remind physicians and other providers to conduct HIV-risk assessments and counseling with outpatient patients in a health maintenance organization setting. In follow-up surveys, patients in the intervention arm reported significantly more discussions of HIV risk and prevention with their physicians . This structural intervention involved a policy change that gave administrative support for the provision of prevention services, including patient education.
Frameworks of factors associated with HIV
Various writers have developed frameworks to differentiate and define levels or types of environmental influences on HIV and other health behaviors (Table 1). Diez-Roux  discussed the impact on public health of the socio-economic status of a population, area-based characteristics such as poverty and deprivation, neighborhood-level characteristics, and treatment-center characteristics. Sweat and Denison  used examples from developing countries to differentiate environmental factors in terms of the range of their influence over HIV-prevention or risk behaviors. According to this framework, superstructural factors such as economic underdevelopment or gender inequality might affect an entire nation. Structural factors such as laws, policies and standard operational procedures might affect the behavior of a segment of the society, such as commercial sex workers or recipients of publicly funded services. Environmental factors might have an impact on the conditions and resources of individuals, such as whether work camps could accommodate the families of male workers. Individual-level factors might influence whether people know about HIV and risk behaviors, and methods to avoid exposure. Tawil et al.  differentiated between individual-level prevention approaches that attempt to persuade individuals to change their HIV-risk behaviors, and economic conditions or policies that may either remove barriers or erect barriers to safe behaviors. Frameworks have also differentiated among social, economic and political types of influence that impact on HIV rates in a society or social subgroups. For example, Mann and Tarantola  introduced the concept of vulnerabilities: HIV risk is affected by personal vulnerabilities, such as individual knowledge and skills; programmatic vulnerabilities, such as education and social services; and societal vulnerabilities, such as discrimination directed at persons with AIDS. Zierler and Krieger  attributed the distribution of HIV among women to inequalities associated with class, race, gender and sexuality.
As shown in Table 1, these frameworks distinguish individual- from structural-level factors that affect HIV prevention. They also describe structural factors as having a more immediate or proximal impact on individuals (at the intermediate level) or a more distal impact (at the macro level). This is an important distinction because it characterizes differing views of HIV experts about how structural factors relate to HIV risk and where interventions need to be targeted. At the macro level, the vulnerability of persons to HIV is influenced by broad social structural characteristics. These 'core' or distal causes may be far removed from individuals' control, but impact their lives through economic inequalities, racism, sexism, discrimination and stigmatization directed towards groups at high risk for HIV. At the intermediate or more proximal level, barriers are more closely linked to specific behaviors, such as when they influence the availability of legal and accessible prevention services or products to reduce the likelihood of infection. This distinction has important implications because the focus of structural research and prevention programming will depend on which level is accepted as causal of HIV outcomes or as the most promising target for interventions. In addition, if the causal link between distal influences and HIV risk is unclear to fund providers and policy-markers, they may be unwilling to support structural research and interventions. The intermediate-level barriers may be easier to study and change, and causal links to HIV risk may be more direct, but they may also fail to address the important core issues. Most of the frameworks shown in Table 1 include both levels.
During 1998, a workgroup of Centers for Disease Control and Prevention staff developed a framework to help define and provide parameters for structural barriers and facilitators of HIV prevention, and a list of barriers or facilitators that might inhibit or support HIV prevention. (Contributing members of the workgroup were Kim Boyd, Scott Damon, Lynda Doll, Patricia Martins, Scott McCoy, Ann O'Leary, Esther Sumartojo, and Linda Wright-Deaguero.) The criteria for barriers and facilitators were that they are part of the context or environment surrounding individuals, but outside their direct control. The workgroup developed a two-dimensional framework of structural factors (see Table 2). One dimension comprised four levels of barriers or facilitators: economic, such as funding to support risk-reduction strategies; policy, including laws and regulations; societal, including community norms, cultural beliefs, and expressions of broad social attitudes such as discrimination or stigmatization targeting specific groups; and organizational, including the structures and functions of service organizations or their capacity to sustain prevention programs. The second dimension comprised the systems that implement and support each type of structural barrier or facilitator: government (of all types); service organizations such as community-based organizations, professional or nonprofit organizations; business or for-profit organizations; workforce organizations such as labor unions; faith communities or organizations such as individual religious institutions or denominations; justice systems such as courts or law-enforcement systems; media organizations; educational systems such as school districts or universities; and healthcare systems such as provider organizations or hospitals.
The Centers for Disease Control and Prevention framework is not meant to be exhaustive, but to provide a model of the scope and character of structural factors related to HIV prevention. For example, an economic barrier to HIV prevention erected by a state or federal government might be limitations on funding for HIV prevention and treatment in prisons. A business-related policy that could facilitate HIV prevention might be self-imposed controls by chemical producers on the sale of products used in 'street' or illicit drugs. A societal barrier to HIV prevention might be promulgated by a community where institutions such as schools, churches, and the police fail to address discrimination or stigmatization directed at men who have sex with men. At an organizational level, a facilitator of HIV prevention through a healthcare system might be the integration of HIV and sexually transmitted disease treatment services, or a requirement that providers discuss HIV testing and prevention with their patients. These facilitators and barriers would be indirectly related to HIV prevention behaviors on the part of individuals but would help to create an environment that supports or inhibits prevention.
Despite the differences among the frameworks described in this article, there appears to be consensus that effective prevention will require a continuum of approaches targeting the structures and environments that influence individual behavior. Consistent terminology, clear explanations of how structural factors influence individual behavior, and realistic ideas for structural and environmental intervention strategies are needed. In particular, research must hypothesize and demonstrate causal relationships between changes in structural conditions and HIV outcomes.
Issues related to structural approaches to HIV prevention
Even if they are meant to facilitate prevention, structural interventions may be seen by some as limiting individual choice or coercing individuals in unacceptable ways. For example, a law to quarantine infected persons, although structural, would be considered an unacceptable loss of individual rights. Laws to remove private rooms in bathhouses have met with strong opposition, partly for this reason . When it was first introduced, named reporting of partners of HIV-infected persons raised concerns about loss of confidentiality [60,61]; this policy has now met greater acceptance as it helps public-health officials identify and offer treatment to newly infected persons . Structural interventions may also inadvertently lead to stigmatization if, for example, they call attention to groups at high risk; for example, when restrictions on HIV-infected immigrants lead to stigmatization of national groups or when regulations preventing blood donations increase stigmatization of high-risk groups.
A second issue is that structural approaches require a shift in our thinking about how to change behavior. Many view behavior as personally motivated or resulting exclusively from a person's conscious decisions. The role of the structural environment is therefore often overlooked. In this way, interventions may aim to change an individual's knowledge or motivations without also addressing the root causes or the context that encourages HIV risk .
An additional issue is the difficulty of assessing the impact of structural interventions and describing how they affect behavior. Structural interventions are difficult to evaluate because they do not conform easily to conventional experimental designs, and effects are difficult to measure. Researchers may be hampered by a lack of methodologies for studying the complex relationship between the context of health and health outcomes. The effectiveness of structural approaches will therefore be hard to defend scientifically without new and rigorous research methods.
Structural interventions may also be perceived as going beyond the traditional role of public health. Indeed, this work will require greater participation by experts in organizational structure and function, lawyers, policy analysts, sociologists and others.
A structural perspective needs to be workable, not just idealistic. Otherwise, the area may be so broadly defined that interventions become impossible. Dowsett  stated: "We could easily produce wondrous arguments on the effects of poverty, the impact of structural adjustment policies on public health infra-structure, the effects of global gender inequalities, the universal vulnerability of young people, the oppression of minorities, or the immoral effects of the international drug marketeers. All true, but they would provide little insight into where to start in developing local public health HIV/AIDS/STD policy or useful, on-the-ground, health promotion interventions to prevent infection and to improve the lives of the infected. The challenge is to come up with a macrosocial view that adds to a workable response to the pandemic instead of one that overwhelms our capacity to act."
It is time for HIV research and interventions to address the structures that influence risk or that limit the impact of other prevention strategies. Ideas and justifications for research and programming will emerge from epidemiological observations, the innovative ideas of HIV experts, research reports, and opportunities for natural experiments provided by new laws, regulations, policies and societal changes. Researchers and health officials, with guidance from affected groups and communities, must determine what research is needed and how it should be prioritized, the types of disciplines and expertise needed, the most promising theories or models, and the most appropriate research methods. There is an urgency to these activities because of the power of structural interventions to affect the HIV epidemic.
At the same time, research will be difficult and controversial. It will be challenging to study multiple interacting levels of behavioral causation while also attending to issues of equality and human rights that are usually involved at the level of structural factors and interventions. Taking a structural approach to preventing HIV implies a much broader role for public-health scientists and providers. It will require a shift in perceptions about how to influence HIV risk behaviors, and new and interdisciplinary research methodologies.
In the Soho region of London, there is a pub that serves as a kind of Mecca for epidemiologists. Its namesake, John Snow, ended a cholera outbreak in that region by removing the handle from the pump that had been delivering contaminated water . Snow did not conduct focus groups, distribute pamphlets or hold skill-building seminars in order to motivate residents to avoid using water from that pump. He simply removed the handle, a kind of structural intervention that would probably be impossible today. There is no pump handle to stop HIV, but there are ways to change the environment through the structures affecting HIV risk. Finding, studying and implementing these approaches are some of the most important challenges facing HIV researchers, health providers and affected communities.
The author acknowledges those colleagues who provided recommendations for the development and revision of this paper: Lynda Doll, Steve Jones, Robert Kohmescher, Richard Parker, Dan Wohlfeiler and Richard Wolitski.
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Based on presentations from Structural Barriers and Facilitators in HIV Prevention, a meeting sponsored by the Centers for Disease Control and Prevention on February 22-23, 1999
This publication is sponsored by the Behavioral Intervention Research Branch; Division of HIV/AIDS Prevention; National Center for HIV, STD, and TB Prevention; U.S. Centers for Disease Control and Prevention.
The Editors of this supplement wish to acknowledge the referees who provided peer reviews of the manuscripts.
Statements of individual authors may not reflect the position of the Centers for Disease Control and Prevention.