Basic Overview of Course of Illness and Treatment of HIV/AIDS

Approximately 940,000 persons in North America and about 40 million persons worldwide are infected with HIV. Infection with HIV is a chronic disease that normally runs its course over many years. AIDS is a late-stage manifestation of HIV infection, characterized by increasing viral load of HIV in the blood and declining immune function (as measured by CD4 T cell counts), leading to a broad spectrum of diseases. According to the definition of the Centers for Disease Control and Prevention (CDC), the diagnosis of AIDS is made in an HIV-positive individual who has at least one of 25 AIDS-defining conditions (e.g., Pneumocystis carinii pneumonia [PCP] or HIV-associated dementia [HAD]) or a CD4 T cell count lower than 200 cells per cubic millimeter.

The human immunodeficiency virus has been clearly identified as the cause of AIDS (Barre-Sinoussi et al. 1983; Gallo et al. 1984). This virus invades the nervous system, causes persistent viremia, and weakens the humoral and cellular immune response of most infected people. HIV has a remarkably complex viral genome, which probably underlies its profound pathogenicity (Varmus 1988).

First identified in 1983, HIV contains ribonucleic acid (RNA) as its genetic material, as well as the enzyme reverse transcriptase, which is required to translate viral RNA into deoxyribonucleic acid (DNA) so that it can use the host cell's nucleic material to replicate. The replicated virus particles, initially strung together, must be split apart by the protease enzyme before they are extruded from the host cell in order for them to become functional and damaging to the immune system.

HIV mutates rapidly, making drug resistance a major problem and contributing to the difficulties in producing an effective vaccine. HIV-1 is the form of the virus that is the causative agent of disease in the United States and much of the rest of the world, but another strain, HIV-2, occurs in West Africa, with scattered cases appearing recently in Asia. HIV-2 is associated with considerably slower disease progression than HIV-1.

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Having either virus does not alter the vulnerability for infection with or confer humoral protection to the other strain (Warner 1997). Some experts estimate that efforts to develop an effective HIV vaccine may be successful within the next 5 to 10 years.

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