Human immunodeficiency virus

• Causes acquired immune deficiency syndrome (AIDS) 

  Weakens immune system - person more susceptible to infection by other microorganisms 
• Transferred when body fluid from one person enters bloodstream or comes in contact with mucous membranes of another 

  Fluid able to carry enough HIV to be infection : 

  • Blood (incl. menstrual blood)
  • Seminal fluid (incl. Pre-ejaculatory fluid)
  • Vaginal and cervical fluid 
  • Breast milk 
• Spread through 

  • Unprotected sexual intercourse 
  • Sharing needles and syringes 
  • From mother to child during pregnancy, childbirth, breastfeeding
  • Blood transfusions
  • Implements that pierce skin if not sterilised 
• Retrovirus - contains RNA core 

  Unable to reproduce by itself
• Infects white blood cells helper (T-lymphocytes) 

  Inside host cells, virus uses enzyme (reverse transcriptase) to turn RNA into DNA

  DNA integrates into lymphocyte’s DNA and produces millions of copies 

  New virus are released into blood to infect more T-lymphocytes 

  Some go into latent stage - able to become active at any stage
• Stages of infection :

  1. Acute infection
  2. Chronic infection
  3. AIDS
• Acute infection

  Person is first infected 

  Virus replicates rapidly 

  Level of HIV in blood is high

  Flu-like symptoms 

  Immune response overcomes infection and patient recovers

  Lasts 2 - 3 weeks 
• Chronic infection 

  Asymptomatic 

  Virus continue to multiply at low rate 

  10 years +
• AIDS

  Developed when immune system has been damaged to the degree it is no longer able to resist other infections 

  High viral load, low level of helper T-lymphocytes
• Diagnosed by detecting presence of HIV antibody in blood 

  • Takes 2 - 12 weeks for antibodies to build up to point where they can be detected 
• Treatment called post-exposure prophylaxis can be given 

  • Course of drugs taken for a month - prevent replication of virus so it doesn't become established 
  • Must be started within 3 days of possible exposure
  • Not 100% effective 

  Number of antiretroviral drugs that inhibit reproductive cycle of virus 

  • Usually given a combination depending on viral load and resistance from previous treatment 
  • Slowing replication and suppressing progression