HIV Infection

Background

• HIV is a retrovirus that was first introduced into humans in Africa around 1920.
• Worldwide prevalence of HIV infection in 2019 was about 38 million people.
• In the United States, approximately 1.2 million persons were living with HIV at the end of 2018, of whom 14% had undiagnosed infection. An estimated 37,515 new HIV infections were diagnosed in 2018.
• Risk of transmission from infected to uninfected persons varies depending on the route of exposure, the viral burden of the transmitting person, and preventative interventions utilized by the infected and uninfected persons at time of interaction.
• Without treatment, HIV infection almost invariably leads to the clinical syndrome of AIDS, which carries a life expectancy of about 3 years from the time of AIDS diagnosis.
• Antiretroviral therapy (ART) can have dramatic benefit for persons living with HIV who can maintain suppressed HIV viral loads.
  • In patients using ART who remain virologically suppressed and maintain CD4 T-cell counts > 500 cells/mcL, survival appears to be almost equivalent to persons without HIV with similar comorbidities.
  • In patients using ART who remain virologically suppressed the risk of transmission is reduced to zero (undetectable = untransmissible).
  • ART before and during pregnancy substantially reduces transmission rates. (See also HIV in Pregnancy.)
• Increasing longevity for persons living with HIV has revealed enhanced risks for non-AIDS-related morbidity and mortality such as cardiovascular, psychiatric, gastrointestinal, and renal disease.
• For HIV-2 considerations, see HIV-2 Infection.

Evaluation

• The Centers for Disease Control and Prevention (CDC) recommends a 3-step testing algorithm involving 2 immunoassays and a confirmatory nucleic acid amplification test. The HIV Western blot is no longer recommended as a confirmatory diagnostic test.
• Patients with HIV infection most often present to health care providers with
  • positive screening test performed at patient request or provider recommendation
  • acute HIV
  • HIV-related opportunistic infection
  • HIV-related malignant neoplasm
• An initial medical evaluation should include:
  • a complete medical history with specific attention to ongoing HIV risk factors, chronic medical and psychiatric conditions.
  • specific focus on current medications including pre- or postexposure prophylaxis (PrEP or PEP), prior antiretroviral exposures, and occupational or nonoccupational exposures relevant to acquisition of opportunistic and nonopportunistic pathogens.
  • a complete physical exam including funduscopic, rectal, and gynecologic examinations when appropriate.
  • laboratory evaluation including complete blood test, electrolytes, kidney and liver function tests, CD4 T-cell count, and HIV viral load, HIV resistance testing, fasting blood glucose, and lipids.
  • screening for sexually transmitted diseases, tuberculosis, hepatitis B and C infections, toxoplasmosis, and cryptococcosis, as well as other endemic fungal diseases as indicated by geographic exposures.
• Provide counseling on the basics of HIV infection, natural history and prognosis, treatment, monitoring of disease activity and progression, and prevention of transmission.
• Assess readiness to start ART based on psychosocial and medical conditions.
• See also Acute HIV Infection.

Management

• ART is recommended for all patients with HIV infection (Strong recommendation).
  • The preferred therapy consists of 1-2 nucleoside reverse transcriptase inhibitors (NRTIs) plus an integrase strand transfer inhibitor.
  • Nonnucleoside reverse transcriptase inhibitors and protease inhibitors are no longer recommended as a first-line therapy but may be preferred in certain situations.
  • Most patients acquire a strain of HIV that is sensitive to all preferred drugs.
    • HIV resistance to ART is uncommon among persons who are able to adhere consistently to prescribed regimens although a small fraction of patients will acquire a drug resistant strain.
    • Patients unable to adhere to their recommended regimen may develop drug resistant HIV.
  • Nonadherence to regimen is the most common cause of treatment failure.
• Opportunistic infections remain a major cause of morbidity in patients with HIV, especially among those who present late in the course of their HIV infection (i.e. CD4 T cell count < 200 cells/mcL), or who are unable to adhere to ART consistently.
  • Tuberculosis
    • Worldwide, tuberculosis remains the major cause of morbidity and mortality among patients with HIV infection, although in the United States, HIV-related TB is uncommon.
    • Testing for latent tuberculosis infection with either a tuberculin skin test or an interferon gamma release assay is recommended for all patients (Strong recommendation).
    • See Latent Tuberculosis Infection in Patients With HIV and Active Tuberculosis in Patients With HIV Infection
  • Other infections for which primary prophylaxis is recommended, based on CD4 T-cell count, include Pneumocystis pneumonia, toxoplasmosis, and disseminated Mycobacterium avium complex infection (Strong recommendation).
• Immunization with vaccines that do not contain live organisms is an important part of disease prevention.

Prevention and Screening

• Screening for HIV is recommended for all persons aged 15-65 years, individuals with risk factors for HIV infection, and all pregnant women, although optimal testing intervals are unknown (Strong recommendation).
• Persons without HIV may benefit from education about approaches to reduce high risk activities, such as unprotected sex or illicit injection drug use.
• Pre-exposure prophylaxis (PrEP) is the use of antiretroviral agents by HIV-uninfected but at-risk individuals in order to prevent acquiring HIV infection prior to exposure.
  • Daily PrEP with recommended regimens reduces the risk of getting HIV from sex by about 99% in patients with detectable drug levels in serum.
  • Among people who inject drugs, daily PrEP with recommended regimens reduces the risk of getting HIV by 74%.
• Postexposure prophylaxis (PEP) is the use of antiretroviral agents by HIV-uninfected but at-risk individuals in order to prevent acquiring HIV infection after occupational and nonoccupational exposures.
• ART use before, during, and after pregnancy can reduce HIV transmission from mother to child. (See HIV in Pregnancy).