lead to treatment failure, and resistance can develop across an entire class of drugs, not just the one currently prescribed, limiting future treatment options. Moreover, the development of drug resistance carries consequences beyond immediate treatment failure. Drug-resistant strains of the virus can be transmitted, compromising effective control of the epidemic and presenting a serious threat to public health. Emerging evidence indicates that the number of newly infected individuals who exhibit drug resistance is growing (Wensing et al., 2003; Grant et al., 2002; Little et al., 2002). Complete viral suppression, obtained through greater than 90 percent adherence, leaves little room for drug resistance to develop. In circumstances of less than total viral suppression, however, the virus begins to select for drug resistance as it replicates and evolves. If a drug-resistant virus is then transmitted, HAART regimens will not be as effective in the newly infected individual. Thus, the best opportunity for delaying development of AIDS will have been lost (Little et al., 2002).

Understanding the dynamics of adherence is an important part of HIV/AIDS care. The DHHS Guidelines list a number of factors that affect an individual’s ability to adhere to a HAART regimen, including active alcohol and substance use and active mental illness (see Box 2-2). The transformation of HIV/AIDS to a chronic disease, which was brought about by the development of HAART, allows for useful comparisons to other chronic illnesses such as diabetes in terms of which factors influence adherence to treatment. The American Public Health Association highlights some of the lessons learned from the diabetes experience that may be useful in promoting adherence to HIV treatments in its Adherence to HIV Treatment Regimens: Recommendations for Best Practices (2002) (see Box 2-3). Among these lessons are that treatment is a collaborative process between patient and provider rather than a directive one from provider to patient, that