HIV -

Epidemiology

ss RNA retrovirus
14 million worldwide positive
Transmission
- 63% homosexual
- 6.6% heterosexual
- 3.5% IV drug users
- Rest are blood transfusion, haemophiliacs, & no cause in 5%

Group	Descriptions
1	Acute infection
2	Asymptomatic infection
3	Persistent generalised lymphadenopathy
4	Other disease A Constitutional B Neurological C Infection D Tumor E Other

Classification of HIV induced disease

CD4 count (T helper cells)
- 500 – average 11 years survival
  - < 200 – Average 2 years survival

2-4 weeks after infection
- Mononucleosis-like illness
- Full recovery usual
- Long period of good health follows

Early Phase (CD4 > 500)
- Autoimmune disorders
  - PGL
  - ITP
  - Guillain-Barre
  - Cranial nerve palsies
  - Sjogrens syndrome
  - Polymyositis
Intermediate Phase (CD4 200-500)
- Mild infections
- Tinea, dermatitis
- Gingivitis
- HSV / Zoster reactivation
Advanced Immune Depletion (CD4 < 200)
- Severe infections, malignancy
- Increased risk of transmission
- Pneumocystis Pneumonia
- Toxoplasma encephalitis
- Cryptococcal meningitis
- CMV retinitis
- Atypical Mycobacterium
- Kaposi sarcoma or NHL

Cellular immunity related
- T Helper Cell primary target
Also impairs
- B lymphocytes
- Monocyte/ Macrophage cell line
- Production of Gamma interferon/ lymphocytes
Impairs wound healing
- Reduced T helper cells & Lymphokines
Reduces platelets
- Autoimmune thrombocytic purpura
Affects bacteriocidal functions of PMN cells
- Chemotaxis
- Phagocytosis
- Secretion of microbicides
Causes neuropathy

ELISA
- Enzyme-Linked Immunosorbent Assay
  - Sensitive but low specificity
Western Blot
- Immunoelectrophoretic test
  - More specific than ELISA
  - Takes longer time & more labour intensive
p24 Antigen
- first two tests look at anti HIV antibody production
- This is positive prior to antibody production thus avoids 3 month window period
- Positive during seroconversion illness