AIDS

 

ACQUIRED IMMUNODEFICIENCY SYNDROME (AIDS)

INTRODUCTION

• AIDS is a chronic, life-threatening condition caused by the Human Immunodeficiency Virus (HIV).
• HIV damages the immune system, especially CD4+ T lymphocytes, reducing the body’s ability to fight infections.
• It is primarily a sexually transmitted infection (STI) but can also spread via blood and from mother to child.
• Without treatment, HIV progresses to AIDS over several years.
• No cure exists, but Antiretroviral Therapy (ART) can control the disease and prolong life.

SYMPTOMS

1. Primary Infection (Acute HIV)

Occurs 2–4 weeks after infection.

Symptoms:

• Fever
• Headache
• Muscle and joint pain
• Rash
• Sore throat
• Painful mouth ulcers
• Swollen lymph nodes

👉 High viral load → highly infectious stage

2. Clinical Latent Stage (Chronic HIV)

• Usually asymptomatic
• May last ~10 years without treatment (longer with ART)

Features:

• Persistent lymphadenopathy
• Virus remains active in lymphoid tissues

3. Symptomatic HIV Infection

Symptoms:

• Fever
• Fatigue
• Chronic diarrhea
• Weight loss
• Oral candidiasis (thrush)
• Herpes zoster (shingles)
• Persistent lymph node enlargement

4. AIDS (Advanced Stage)

Features:

• Severe immunosuppression (CD4 < 200 cells/mm³)
• Opportunistic infections & cancers

Symptoms:

• Night sweats
• Chronic diarrhea
• Persistent fever
• Severe weight loss
• Oral lesions
• Skin rashes

PATHOGENESIS

1.     Entry & Replication

• HIV enters bloodstream → rapid viral replication
• High viral load in early phase

2.     CD4+ T Cell Depletion

• Acute phase:
• Viral destruction + cytotoxic T cell killing
• Chronic phase:
• Immune activation + reduced T cell production

3.     Immune Response

• CD8+ T cells control viral load partially
• Antibodies formed but do not eliminate virus

4.     Mucosal Damage

• Massive loss of CD4 cells in intestinal mucosa
• Due to CCR5 receptors (entry point for HIV)

5.     Progression to AIDS

• Gradual CD4 decline → opportunistic infections

CAUSES & TRANSMISSION

Modes of Transmission:

1. Unprotected sexual contact (vaginal, anal, oral)
2. Blood transfusion (rare due to screening)
3. Sharing contaminated needles/syringes
4. Mother-to-child transmission
• During pregnancy
• Childbirth
• Breastfeeding

DIAGNOSIS

1. Screening Test

• ELISA (Enzyme-Linked Immunosorbent Assay)
• Detects HIV antibodies
• Highly sensitive

Limitations:

• False positives: pregnancy, viral infections, vaccination
• False negatives: early infection (window period)

2. Confirmatory Test

• Western Blot Test

3. Viral Load Tests

• Measure HIV RNA in blood
• Methods:
• PCR (Polymerase Chain Reaction)
• Branched DNA assay

4. CD4 Count

• Normal: 500–1600 cells/mm³
• AIDS: <200 cells/mm³

WHO CLINICAL STAGING

Stage I

• Asymptomatic
• No AIDS

Stage II

• Minor mucocutaneous infections
• Recurrent upper respiratory infections

Stage III

• Chronic diarrhea (>1 month)
• Severe bacterial infections
• Pulmonary tuberculosis

Stage IV (AIDS)

• Opportunistic infections:
• Cerebral toxoplasmosis
• Esophageal candidiasis
• Kaposi’s sarcoma

TREATMENT

Antiretroviral Therapy (ART)

• Combination therapy (HAART)
• Reduces viral load
• Improves CD4 count
• Prevents disease progression

Classes of Anti-HIV Drugs

1.     NRTIs (Nucleoside Reverse Transcriptase Inhibitors)

• Example: Zidovudine, Lamivudine, Tenofovir

2.     NNRTIs (Non-Nucleoside RT Inhibitors)

• Example: Efavirenz, Nevirapine

3.     Protease Inhibitors (PIs)

• Example: Ritonavir, Atazanavir

4.     Entry/Fusion Inhibitors

• Example: Enfuvirtide, Maraviroc

5.     Integrase Inhibitors

• Example: Raltegravir

PREVENTION

1. Safe Sex Practices

• Use condoms
• Limit multiple partners

2. Abstinence

• Most effective prevention

3. Safe Needle Use

• Avoid sharing needles
• Needle exchange programs

4. Blood Safety

• Screening of blood products

5. Healthcare Precautions

• Use PPE (gloves, masks, goggles)
• Proper handling of body fluids

6. Prevention of Mother-to-Child Transmission

• ART during pregnancy
• Safe delivery practices
• Avoid breastfeeding if advised

KEY POINTS FOR EXAMS

• HIV targets CD4+ T cells
• Acute phase = high infectivity
• AIDS defined by CD4 < 200 cells/mm³
• ELISA → screening, Western blot → confirmation
• ART = lifelong treatment
• No cure, but manageable disease