Human immunodeficiency virus (HIV) Flashcards
Define HIV
Retrovirus that replicates in human lymphocytes and macrophages and destroys CD4 T cells, the aetiological agent of acquired immunodeficiency syndrome (AIDS)
What are the type of HIV
HIV 1: global epidemic
HIV 2: less pathogenic and restricted mostly to West Africa
Aetiology of HIV
Retrovirus that infects and replicates primarily in human CD4+ cells and macrophages
Transmission via blood, blood produces, sexual fluids and other fluids containing blood and breast milk
Sexual intercourse is the most common but most inefficient mode of transmission (Risk of transmission 0.1% per contact, heterosexual)
Others before birth or during delivery, during breastfeeding or when sharing contaminated needles and syringes (IVDU)
Risk factors for HIV
Needle sharing with IVDU
Unprotected receptive anal intercourse
Unprotected receptive penile-vaginal sexual intercourse
Percutaneous needle stick injury
High maternal viral load (vertical transmission)
Use of progestin-only injectable contraceptives, HSV-2 infection
Epidemiology of HIV
37 million people living with HIV at the end of 2018
70% of those with HIV are in sub-Saharan Africa
Transmission among heterosexuals was the largest single route of infection in 2017
What are the phases of HIV infection
Phase 1: Primary infection / Seroconversion (4-8 weeks post-infection):
- Self limiting | Fever | Night sweats | Generalised lymphadenopathy | Sore throat | Oral ulcers | Rash | Myalgia | Headache | Encephalitis | Diarrhoea
Phase 2: Early / Asymptomatic (18 months – 15+ years)
- Appears well | Persistant lymphadenopathy (>1cm node at 2+ extrainguinal sites for >3months) | Progressive minor symptoms: rash, oral thrush, weight loss, malaise
Phase 3: AIDS (~6-9 years)
- Syndrome of secondary diseases reflecting severe immunodeficiency or direct effect of HIV infection
- Constellation of opportunistic infections, conditions or malignancy that occur due to HIV infection
- CD4 cell count < 200 / mm3
What are the direct effects of HIV infection
Neurological: Polyneuropathy | Myelopathy | Dementia
Lung: Lymphocytic interstitial pneumonitis
Heart: Cardiomyopathy | Myocarditis
Haematological: Anaemia | Thrombocytopenia
GI: Anorexia | HIV enteropathy (malabsorption and diarrhoea) | Severe wasting
Eyes: Cotton wool spots
What tumours are associated with HIV
Kaposi’s sarcoma (cutaneous or conjunctival vascular tumour caused by human herpesvirus [HHV8])
Squamous cell carcinoma (particularly cervical or anal)
Non-Hodgkin’s B-cell lymphoma (brain, GI)
Hodgkin’s lymphoma
Investigations for HIV
- ELISA (confirm with Western blot): +ve
- Serum HIV rapid test: +ve
- Serum HIV DNA PCR: +ve
- CD4 count: <200 = AIDS
- Serum viral load (HIV RNA): millions when acute/end stage, thousands during control
Drug resistance test Serum hep B/C: serology Treponema pallidum: +ve in syphilis Tuberculin skin test: ?TB FBC: Anaemia/thrombocytopenia Lipid profile: ART associated with raised cholesterol Glucose: elevated n patients on ART
