people experience the acute retroviral syndrome, which is flu-like illness characterized by nonspecific symptoms such as fever, fatigue, rash, musculoskeletal pain, sore throat, swollen lymph nodes, arthralgias or myalgias, pharyngitis, and lymphadenopathy (Fauci et al., 1996). During this time, test for HIV antibody tests are usually negative and infection can only be diagnosed by testing the blood for viral products such as HIV RNA (viral load) or proteins (P24 antigen) (Pantaleo et al., 1993; Fauci et al., 1996). After the acute phase of infection, the amount of viral products in the blood is reduced, and tests for HIV antibody become positive. Patients then enter a prolonged period, usually 10 or more years, during which they have no (or perhaps few) symptoms despite the fact that HIV continues to actively multiply. Because of this, persons can still transmit the virus to others during the asymptomatic phase, allowing HIV to spread unnoticed (IOM/NAS, 1988; Pantaleo et al., 1993).
The ongoing multiplication of HIV causes progressive damage to a person’s immune system through destruction of specific white blood cells known as CD4+ T-lymphocytes. With the progressive decline in CD4+ cell count, most infected persons eventually begin to develop symptoms which can include syndromes such as fever, unexplained weight loss, diarrhea, and dementia (Pantaleo et al., 1993). The damage to their immune system predisposes them to a wide range of unusual diseases. These so-called opportunistic conditions include infections with nonaggressive microorganisms and certain cancers. When these conditions occur in the presence of HIV infection or when the CD4+ cell count drops below 200 cells/µL, the patient is said to have developed AIDS. In the absence of treatment, the disease is nearly always fatal with the median time from a CD4+ count < 200 cells/µL to death of 3.7 years in an untreated patient (Pantaleo et al., 1993). To date, no cure or vaccine has been developed for HIV disease, although recent treatment advances in combination antiretroviral therapy have resulted in slowing of the progression of the disease, and often temporary restoration of immune functioning, in infected individuals.
The AIDS epidemic, now entering its third decade, has had an enormous impact in terms of morbidity and mortality. By the end of 2001, 816,149 AIDS cases and 467,910 deaths had been reported in the United States to the CDC (CDC, 2002). AIDS prevalence has increased steadily over time; at the end of 2001, an estimated 362,827 people were living with AIDS (CDC, 2002). Globally, an estimated 40 million people are living with HIV/AIDS and three million people have now died from AIDS (CDC, 2002).