• HIV is a retrovirus (subgroup lentivirus) that integrates into CD4 T lymphocytes, altering cell-mediated immunity and causing cell death, severe immunodeficiency, opportunistic infections, and malignancies if not treated.
  • The natural history of untreated HIV infection includes viral transmission, acute retroviral syndrome, recovery and seroconversion, asymptomatic chronic HIV infection, and symptomatic HIV infection or AIDS.
  • Without treatment, the average patient progresses to AIDS ~10 years after acquiring HIV. Without treatment, people living with full-blown AIDS typically survive about 3 years.



  • ~30,500 people aged >13 years were diagnosed with HIV in the United States during 2020. The incidence decreased by 8% from 2016 to 2019.
  • There were approximately 1.5 million new cases of HIV worldwide in 2020 (1).


  • As of 2019, ~1.2 million persons in the United States have HIV; ~13% are not aware that they are infected (1).
  • As of 2020, ~38 million people are living with HIV worldwide. ~45% of new diagnoses are in Eastern and Southern Africa (1).
  • In 2020, ~680,000 people died from AIDS-related illnesses (1).

Etiology and Pathophysiology

  • HIV primarily infects CD4+ cells. HIV is a single-stranded, positive-sense, enveloped RNA virus. After entering target cells, viral RNA is transcribed to DNA (through reverse transcription), imported to the host cell nucleus, and incorporated into host DNA. The virus can become latent or produce new viral RNA with proteins that are released to infect other CD4+ cells. Host CD8+ cells are activated as part of the seroconversion response.
  • There are two types of HIV. HIV-1 causes the majority of HIV infections. HIV-2 is less infectious and seen primarily in West Africa.

Risk Factors

  • Sexual activity (>90% of transmission): Receptive anal sex is the highest risk. Ulcerative urogenital lesions promote transmission (1).
  • Injection drug use
  • Children of HIV-infected women: Maternal HIV-1 RNA level predicts transmission.
    • HIV can also be transmitted in breast milk. HIV+ women should not breastfeed, unless there is no alternative. In this case, consider antiretroviral therapy (ART).
  • Recipients of blood products prior to 1985
  • Occupational exposure (health care workers)

General Prevention

  • Primary prevention: behavioral counseling for all sexually active people with high risk of STIs (2)
    • Avoid unprotected, high-risk sex, and injection drug use, especially shared needle
    • Condom use reduces risk of transmission by 77–80%.
  • Preexposure prophylaxis (PrEP) is recommended by WHO and USPSTF for persons at high risk of acquiring HIV.
    • General guidelines for PrEP: (i) exclude acute or chronic HIV infection before initiating therapy, (ii) repeat HIV testing every 3 months during therapy, (iii) renal and liver function testing at baseline, 2 to 8 weeks after initiating PrEP, and every 6 months
  • Postexposure prophylaxis (PEP) should be started within 72 hours of exposure and continued for 28 days with a three-drug regimen.
  • For HIV+ patients using ART, maintaining HIV RNA levels <200 copies/mL prevents risk of transmission to sexual partners (treatment as prevention) (3)[A].
  • CDC recommends screening for HIV at least once in patients aged 13 to 64 years.
  • Pregnant women should be tested at the initial prenatal visit and again during the 3rd trimester (2).
  • At least annual screening is recommended for patients at higher risk (2).

Commonly Associated Conditions

  • Other sexually transmitted infections
  • Syphilis, tuberculosis, and hepatitis (B or C) can be more aggressive in HIV-infected persons.
  • Increased risk for cervical cancer, lymphoma, and skin malignancies

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