Note that HIV is also covered in the eLearning Core Knowledge tutorial on Sexually Transmitted Infections.
HIV is a retrovirus that contains the enzyme reverse transcriptase. This enzyme allows the virus to transcribe its RNA genome into DNA, which it then integrates into the host cell DNA. Infection is then permanent.
Aetiology
HIV targets lymphocytes, which express CD4 molecules on their surface. When the virus is active it results in the destruction of CD4 lymphocytes and progressive immunosuppression.
Transmission
Transmission of HIV occurs via:
- sexual intercourse
- intravenous drug use
- transfusion of blood and blood products
- during pregnancy and breastfeeding (vertical transmission).
In 2011, the prevalence of HIV among pregnant women in the UK was 2.2 per 1000 women. The majority of these women were from sub-Saharan Africa (2–3%).
Implications
The risk of vertical transmission of HIV is between 25% and 40% in breastfeeding African populations. Vertical transmission rates of less than 2% have been reported with the use of highly active anti-retroviral therapy (HAART), appropriate management of delivery and avoidance of breastfeeding. In the UK, the risk of vertical transmission for women who take HAART and avoid breastfeeding is 1%. The transmission rate for women on cART and undetectable viral load is at the lowest at 0.57%.
