HIV/AIDS

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Description

HIV is a retrovirus that integrates into CD4 T lymphocytes, altering cell-mediated immunity and causing cell death, severe immunodeficiency, opportunistic infections, and malignancies if not treated. Untreated HIV infection typically advances through several stages: viral transmission, acute retroviral syndrome, recovery, seroconversion, and then chronic infection, leading (an average of 8 to 10 years later) to AIDS.

Epidemiology

Incidence

There were approximately 1.3 million new cases of HIV worldwide in 2022, including an estimated 31,800 new infections in the United States, the latter reflecting a 12% decrease from 2018. The year 2022 saw 37,981 individuals aged ≥13 years diagnosed with HIV in the United States and its territories, comprising both new and preexisting infections.

Prevalence

There were approximately 1.2 million persons with HIV (PWH) in the United States in 2022: ~13% unaware of their status. HIV continues to disproportionately affect certain populations, particularly racial and ethnic minorities and men who have sex with men (MSM). Globally, there were an estimated 38 million PWH in 2022.

Etiology and Pathophysiology

HIV is a single-stranded, positive-sense, enveloped RNA lentivirus that primarily infects CD4+ cells. After entering target cells, viral RNA is transcribed to DNA through reverse transcription, imported into the host cell nucleus, and integrated into host DNA. The virus can become latent for many years, or when the CD4+ cell is activated, produce new viral RNA and proteins that are packaged and released to infect other CD4+ cells. Of its two subtypes, HIV-1 causes most infections, whereas HIV-2 primarily found in West Africa.

Risk Factors

Most people acquire HIV through anal or vaginal sex or by sharing needles, syringes, or other drug injection equipment. Only certain body fluids can transmit HIV, primarily semen, blood, human milk, vaginal or rectal fluids, and cerebrospinal fluid (CSF). Urine, feces, saliva, and sweat do not transmit HIV unless visibly contaminated with blood. Perinatal transmission can occur during pregnancy, childbirth, and nursing (breastfeeding).

General Prevention

  • Everyone aged 13 to 64 years (CDC) or 15 to 65 years (USPSTF) once in a lifetime (more often if risk factors). All pregnant people should be screened at the first prenatal visit and again in the 3rd trimester if at high risk or in a high-prevalence area. STIs increase susceptibility to HIV infection, so testing for HIV must be considered whenever diagnosing and treating STIs.
  • Behavioral interventions, including counseling for at-risk populations, are recommended to reduce high-risk behaviors. Consistent and correct use of condoms during sexual activity reduces transmission.
  • Harm reduction strategies for people who inject drugs, such as needle and syringe exchange programs and use of sterile injection equipment, are effective.
  • Treatment as prevention (TasP): PWH with viral suppression on antiretroviral therapy (ART) are not infectious to their sexual partners. Early diagnosis and initiation of ART in PWH reduces community viral load and transmission risk.
  • Preexposure prophylaxis (PrEP) with antiretroviral medications are highly effective and recommended by USPSTF for individuals at substantial risk, including MSM, transgender women, heterosexuals with high-risk exposures, and people who inject drugs.
  • Postexposure prophylaxis (PEP): Taking 28 days of full ART after an HIV exposure is highly effective at preventing HIV transmission.

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