Human Immunodeficiency Virus (HIV)

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management

Definition

Human Immunodeficiency Virus (HIV) is a chronic viral infection that targets the immune system, specifically CD4+ T cells, leading to immunosuppression and increasing susceptibility to opportunistic infections.

Aetiology

  • Caused by the Human Immunodeficiency Virus, belonging to the retrovirus family.
  • Two main types: HIV-1 (most common) and HIV-2 (less virulent, mainly in West Africa).
  • Transmitted via blood, sexual contact, perinatal transmission (mother to child), and shared needles.

Pathophysiology

  • HIV binds to CD4+ T cells via the gp120 envelope protein.
  • Virus integrates into host DNA using reverse transcriptase and replicates, leading to gradual CD4 depletion.
  • Progression to Acquired Immunodeficiency Syndrome (AIDS) occurs when CD4 count drops below 200 cells/µL or opportunistic infections arise.

Risk Factors

  • Unprotected sexual intercourse.
  • Multiple sexual partners.
  • Sharing of needles or injecting drug use.
  • Blood transfusions (rare due to screening).
  • Mother-to-child transmission during pregnancy, childbirth, or breastfeeding.

Signs and Symptoms

  • Acute HIV infection (seroconversion illness):
    • Fever, lymphadenopathy, sore throat.
    • Maculopapular rash.
    • Myalgia, headache.
  • Chronic HIV (clinical latency):
    • Asymptomatic or mild non-specific symptoms.
    • Persistent generalised lymphadenopathy.
  • AIDS:
    • Opportunistic infections (Pneumocystis jirovecii pneumonia, TB, candidiasis).
    • Malignancies (Kaposi’s sarcoma, lymphoma).
    • Neurological complications (HIV encephalopathy, progressive multifocal leukoencephalopathy).

Investigations

  • HIV antigen/antibody test: detects p24 antigen and anti-HIV antibodies.
  • HIV RNA PCR: confirms diagnosis in early infection.
  • CD4 count: assesses immune function and disease progression.
  • HIV viral load: monitors treatment response.
  • Screening for co-infections: TB, hepatitis B/C, syphilis.

Management

All management is led by specialist services.

1. Antiretroviral Therapy (ART):

  • First-line regimen: combination of two nucleoside reverse transcriptase inhibitors (NRTIs) + integrase strand transfer inhibitor (INSTI).
  • Common regimen: tenofovir + emtricitabine + dolutegravir.
  • ART should be initiated in all patients regardless of CD4 count.

2. Opportunistic Infection Prophylaxis (specialist management):

  • Co-trimoxazole for Pneumocystis jirovecii pneumonia (CD4 <200 cells/µL).
  • Azithromycin for Mycobacterium avium complex (CD4 <50 cells/µL).

3. Preventative Measures (to prevent HIV transmission often done at sexual health clinics):

  • Pre-exposure prophylaxis (PrEP) for high-risk individuals.
  • Post-exposure prophylaxis (PEP) within 72 hours of exposure.
  • Routine screening in high prevalence populations.

4. Psychosocial and Supportive Care:

  • Education on transmission prevention.
  • Psychological support and counselling.
  • Address stigma and social issues affecting quality of life.

5. Referral:

  • Infectious diseases: for ART initiation and management.
  • Respiratory medicine: for HIV related pneumonia.
  • Oncology: for HIV associated malignancies.
  • Psychology: for mental health support.
Infectious DiseasemypanotesHuman Immunodeficiency Virus (HIV)