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DEFINITION AND HISTORY

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  • Patients with serologic evidence of infection with the human immunodeficiency virus (HIV) can be diagnosed as having acquired-immunodeficiency syndrome (AIDS) based upon "clinical" or "immunologic" criteria (see Table 52–1).

    — Patients with AIDS diagnosed based on clinical criteria are classified as having "clinical AIDS."

    — Patients with AIDS diagnosed based on a blood CD4 T cell count of less than 200/μL are classified as having "immunological AIDS."

  • Patients with HIV are living longer in the era of highly active antiretroviral therapy (HAART).

  • United Nations estimated that 30 to 35 million people worldwide were living with HIV infection in 2007, with the majority being infected by heterosexual contact.

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Table Graphic Jump Location
TABLE 52–1DEFINITION OF AIDS IN THE UNITED STATES
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ETIOLOGY AND PATHOGENESIS

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Human Immunodeficiency Virus 1

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  • The primary cause of AIDS is infection with HIV-1.

  • HIV-1 is a member of the Lentivirinae subfamily of retroviruses.

    — Retroviruses are RNA viruses that induce a chronic cellular infection by converting their RNA genome into a DNA provirus that is integrated into the genome of the infected cell.

  • Infection by these lenetviruses is characterized by long periods of clinical latency followed by gradual onset of disease-related symptoms.

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Transmission of HIV

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  • The four main routes of HIV infection are:

    • Sexual contact with an infected partner.

      • The risk for HIV transmission through sexual contact may be increased in persons with other concurrent sexually transmitted diseases.

    • Parenteral drug use.

      • Sharing needles and syringes is the main mode of transmission.

    • Exposure to infected blood or blood products.

      • Ninety percent of those who receive a contaminated unit of blood become infected.

      • Risk of HIV transmission through transfusion of a unit of red blood cells tested negative for antibodies to HIV is approximately 1 in 493,000 transfusions.

    • Perinatal exposure.

      • HIV-1 may be transmitted in utero, intrapartum (at the time of delivery) or postpartum, through ingestion of HIV-1-infected mother's milk.

      • The risk of infection from mother to infant differs in various parts of the world, ranging from approximately 15 percent in Europe and approximately 40 to 50 percent in Africa.

      • The risk of perinatal transmission is increased from mothers with more advanced HIV disease, higher HIV-1 viral load in the plasma, or a history of cigarette smoking and/or active drug abuse.

      • Antiretroviral agents in pregnancy and delivery, with subsequent administration to the infant for the first 6 weeks of life, has resulted in a dramatically reduced rate ...

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