Human Immunodeficiency Virus Infection
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- HIV-1 and HIV-2 are the etiologic agents of HIV infection and AIDS. Infection is lifelong.
- HIV-1 is more common worldwide, whereas HIV-2 is mainly prevalent in West Africa.
- Typically, an acute phase with flulike symptoms develops 2–4 weeks after acquiring infection, followed by a long asymptomatic period (5–15 years in adults, shorter in children), then the development of nonspecific signs and symptoms (weight loss, adenopathy, hepatosplenomegaly, failure to thrive) and mild clinical immunodeficiency.
- Without treatment, the infected person will experience progressive immunologic deterioration and eventually become susceptible to opportunistic infections and cancers (AIDS).
- HIV infection is almost completely preventable.
- Risk of transmission to newborns of HIV-infected women can be decreased:
- With antenatal 3-drug regimens, delivery via elective cesarean section for selected cases, and 6 weeks of postnatal zidovudine, perinatal transmission rates are now 2% or less in HIV specialty care sites.
- All pregnant women should be offered HIV testing at the first prenatal visit. In areas of high incidence, repeat testing should be done at 36 weeks of gestation.
HIV infection is transmitted via the following:
- Sexual contact
- Male-to-female transmission more efficient than female to male
- Anal receptive sex more likely to transmit than vaginal sex
- Exposure to infected blood or bodily fluids
- Usually parenteral exposure to infected blood (via transfusions or sharing needles)
- Risk of transmission from an HIV-contaminated needle is 1/300.
- Breast milk
- Overall risk of breastfeeding is ∼15%.
- In countries where breastfeeding is the norm, up to 30% of perinatally acquired HIV infections occur through breastfeeding.
- Perinatal infection can occur either in utero or during labor and delivery:
- Of perinatally infected infants, 5–10% are believed infected in utero, whereas ∼20% acquire infection around the time of birth.
- Risk of an HIV-infected mother (not on treatment) giving birth to an infected infant is ∼20% (in the absence of breastfeeding), with increased rate of transmission for women with low CD4 counts or higher viral titers. Vaginal delivery, especially with rupture of membranes >8 hours, appears to increase the risk of infant infection.
- Presence of untreated sexually transmitted infections (STIs), chorioamnionitis, and prematurity all increase the risk of mother-to-child transmission of HIV.
- HIV is not believed to be transmitted by the following:
- Sharing utensils, bathrooms, bathtubs
- Exposure to urine, feces, vomitus (except where these fluids may be grossly contaminated with blood, and even then transmission is rare, if it happens at all)
- Casual contact at home, school, or day care center