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Source: Anderson PL, Kakuda TN, Fletcher CV. Human immunodeficiency virus infection. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic Approach. 10th ed. New York, NY: McGraw-Hill; 2017. Accessed April 10, 2017.


  • Infection caused by HIV virus.

    • Hallmark of HIV disease depletion of cluster of differentiation 4 (CD4) cells and associated development of opportunistic infections and malignancies.


  • HIV an RNA retrovirus, types HIV-1 and HIV-2.

    • HIV-1: Predominant virus worldwide1

    • HIV-2: western Africa2


  • HIV infects cells expressing CD4 (T-helper cell) receptors, such as:

    • T-helper lymphocytes.

    • Monocytes.

    • Macrophages.

    • Dendritic cells.

    • Brain microglia.

  • Unrelenting destruction of CD4 cells causes profound immunosuppression and AIDS.

  • RNA-dependent DNA polymerase (reverse transcriptase) transcribes RNA into DNA.

  • Double-stranded DNA migrates into nucleus and is integrated into host-cell chromosome.

    • HIV can establish persistent, latent infection, inhibiting cure.

  • HIV replicates in activated cells.

  • Three phases of viral replication and pathogenesis:

    • Acute (2–3 weeks)

    • Chronic (several years)

    • Terminal (acquired immunodeficiency syndrome [AIDS])


  • Infection occurs through 3 primary modes:

    • Sexual: Most common method for transmission, primarily anal and vaginal intercourse.

      • Highest risk from receptive anal intercourse at an estimated per-act probability of 138 per 10,000 exposures3

      • Condom use reduces risk of transmission by approximately 80%.3

      • Individuals with genital ulcers or sexually transmitted infections (STIs) at great risk.

    • Parenteral.

      • Infected blood exposure from needle sticks, IV injection with used needles, receipt of blood products, and organ transplants.

      • Risk of transmission from needle sharing is at an estimated per-act probability of 63 per 10,000 exposures.3

    • Perinatal.

      • Most infections occur during or near time of birth.

      • Frequency of breast milk transmission is 5–10% in the first 6 months and 15–20% in through 18–24 months for an overall risk of 30–45%.4

  • Revised classification system for adult and child HIV found in Table 1.

TABLE 1.Surveillance Case Definition for HIV Infection Stage Based on CD4+ T-lymphocyte Counts, United States, 2014

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