HIV Infection: Etiology and Epidemiology

HIV Infection

• Global situation and trends:
  • Over 70 million people infected with HIV virus
  • About 35 million people died of AIDS
  • 37 million people living with HIV at the end of 2015
  • Male > female (70%)
  • African American & Hispanics affected more
• Use of antiretroviral drugs:
  • Slowed progression of HIV to AIDS and prolonged life span
  • Changed from fatal disease to chronic illness in industrialized countries
  • People living to old age and children living into adulthood

HIV Transmission

• Risk factors:
  • Sexual practices (unprotected sex, multiple sexual partners, anal or oral sexual activity)
  • Improper condom use
  • Open sores, lesions, or irritation in genital area
  • Body fluids, blood, urine, semen
  • IV drug users
  • Women infected - transmitted thru gestation, delivery, breast milk (rare)
• Not transmitted by:
  • Casual contact
  • Sneezing, cough, toilet seats, bathtub, swimming pools, dishes, utensils, linens of infected person
  • Biting or blood sucking insects
  • Blood transfusions (not significant source of infection; HIV screening done since 1985)

Primary Infection

• Manifestations:
  • Dramatic burst of HIV activity with high viral load and decrease in CD4 count
  • 50%-70% of persons have symptoms of flu-like syndrome, but do not relate to HIV
  • Diagnosis often missed by primary care provider
• CDC recommends HIV testing for all patients between ages 13 to 64 in all health care settings (no separate consent required)

AIDS

• HIV is an acquired infection that:
  • Integrates itself into CD4 (T4) helper cells
  • Causes severe immune dysfunction, rendering the infected person susceptible to life-threatening infections and malignancies
  • Results in acquired immunodeficiency syndrome (AIDS)
  • Remains incurable

Diagnostic Tests

• ELISA blood test: sensitive for HIV 1 antibodies
• Western Blot: confirmation test for HIV
• CD4 counts and HIV viral loads can be used to diagnose AIDS and evaluate treatment

Stages of HIV

Secondary Stage

• May last 10 years; course of illness varies from person to person
• Pt. free from major symptoms; as viral load increases, CD4 cell count declines
• Virus in lymph; viral load test done; high viral load and low CD4 count do not correlate with physical signs
• AIDS exists when CD4 cell count drops below 200 per microliter of blood and opportunistic infections occur

Stage 3: Symptomatic HIV Infection

• HIV crosses blood-brain barrier and causes encephalopathy
• Opportunistic infections affect:
  • Respiratory system (Pneumocystis Carinii pneumonia, TB, Kaposi's sarcoma)
  • GI system (Candida, CMV or cytomegalovirus, cryptosporidiosis)
  • CNS (toxoplasmosis, cryptococcosis, varicella zoster, herpes simplex)

Stage 4: HIV

• HIV wasting syndrome: weight loss of 10-15%
• Other opportunistic infections occur
• Pneumocystic carinii pneumonia: prophylaxis should start when CD4 count is less than 200 to 300 cells/mm3
• Toxoplasmosis of brain
• Candidiasis esophagus, trachea, bronchi
• Herpes simplex virus infection
• Extra pulmonary TB
• Lymphoma
• HIV encephalopathy and dementia, blindness, death

Opportunistic Infections

• Cause clinical manifestations of HIV
• Symptoms: chills, fever, night sweats, dry productive cough, dyspnea, confusion, seizures, headache, malaise, fatigue, oral lesions, skin rash, abdominal discomfort, diarrhea, weight loss, lymphadenopathy, progressive generalized edema

Immunologic Manifestations of AIDS

• CD4 count: used to measure extent of immune damage that has occurred as a result of infection and complications
• Used to monitor antiretroviral therapy
• Used in conjunction with viral load to predict possibility of viral progression, determine when to start therapy, and monitor effectiveness of treatment

HAART (Highly Active Antiretroviral Therapy)

• Protease inhibitors combined with 2 other drugs (reverse transcriptase inhibitors and non-reverse transcriptase inhibitors), forming a "cocktail"
• Decrease viral load by disrupting HIV at different stages of replication
• Serious side effects: require oversight by primary care provider and high level of compliance

HIV and Opportunistic Infections

• Occur with a variety of organisms due to profound immunosuppression of person with AIDS
• Opportunistic infections may result from primary infections or reactivation of latent infection
• May have more than 1 infection at one time
• HAART therapy is the most effective way to prevent opportunistic infections associated with HIV

Focus:

• Risks
• Signs and symptoms
• Patient teaching