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  • Table 41-1 presents the case definition for adult, adolescent, and children, respectively, for human immunodeficiency virus (HIV) infection.

TABLE 41-1Surveillance Case Definition for HIV Infection Stage Based on CD4+ T-Lymphocyte Counts, United States, 2014


  • Infection with HIV occurs through three primary modes: sexual, parenteral, and perinatal. Sexual intercourse, primarily anal and vaginal intercourse, is the most common vehicle for transmission. The highest risk appears to be from receptive anorectal intercourse at about 1.4 transmissions per 100 sexual acts. Condom use reduces the risk of transmission by approximately 80%. Individuals with genital ulcers or sexually transmitted diseases are at great risk for contracting HIV.

  • Heterosexual transmission is the most common mode of transmission in sub-Saharan Africa and worldwide (∼80% of cases).

  • The risk of HIV transmission from sharing needles is approximately 0.67 per 100 episodes.

  • Healthcare workers have a small risk of occupationally acquiring HIV, mostly through accidental injury, most often percutaneous needlestick injury. Mucocutaneous exposures (eg, tainted blood splash in eyes, mouth, or nose) carry a transmission risk of approximately 0.09%.

  • Perinatal infection, or vertical transmission, is the most common cause of pediatric HIV infection. The risk of mother-to-child transmission is ∼25% in the absence of antiretroviral therapy. Breast-feeding can also transmit HIV.


  • The natural history of HIV infection exhibits three general phases: acute, chronic, ...

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