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Transmission of HIV

  • Sharing needles:
    • i.e drug users
  • Unprotected Sex:
    • the virus cnan enter the bloodstream of a sexual partner through breaks in the skin
    • common in people who have other STI's as it can enter throught lesions, which are caused my the other infections
    • can also occur via oral sex, but uncommon
  • Direct blood-to-blood transfer:
    • through cuts and grazes
  • Maternal transmission:
    • from mother to unborn child or in breast milk
    • risk is in the last few weeks of preganancy, especially during birth, as it's the most likely time for infant and maternal blood to meet
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  • Acquired Immune Deficiency Syndrome
  • Caused by infection of HIV, the virus infects and slowly destroys the cells in the body that usually fight infections
  • leaves the body suceptible to disease it would normally be able to combat
  • Without treatment, the immune system will be too weak to fight off illness, and a person may develop rare infections or cancers
  • When the infections become especially serious the person is said to have AIDS


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HIV invasion

  • As soon as HIV enters the body, your immune system starts to produce antibodies to the virus.
  • Antibodies are not able to kill HIV. As HIV makes copies of itself (multiplies) in your blood, it attacks your immune system.
  • HIV attacks CD4 cells, a type of cell that fights infection. CD4 cells are also called the T helper cells, or T cells.
  • Once HIV is in the body, the virus invades CD4 cells and makes copies of itself inside these cells.
  • These new copies of the virus are let out into the bloodstream and go on to attack other CD4 cells.
  • The CD4 cells then die. This process is repeated over and over, killing more CD4 cells.
  • As CD4 cells are attacked and destroyed by HIV, the immune system grows weak. This makes it harder for your body to fight infection and disease, such as pneumonia, herpes, and tuberculosis, and certain cancers (lymphoma and cervical cancer).
  • As the CD4 count goes down, the amount of HIV in the blood goes up. The amount of HIV in a sample of blood is called viral load.
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AIDS- course of the disease

  • AIDS doesn't always follow HIV, there are several stages int he course of the disease once someone is infected, and they depend on several factor, i.e.:
    • Health of host before infection
    • Genetic resistance to host of infection
    • Quality of host's immune response to initial infection
    • Their lifestyle and nutrition
    • The availabilty of a good health care system to them
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The Acute Phase

  • HIV antibodies appear in the blood after 3-12 weeks
  • Infected person may experience symptoms such as fever, sweats, headache, sore throat and swollen lymph nodes
  • Sometimes people show no symptoms at all
  • Rapid replication of the virus in the blood and the loss of T helper cells begins
  • After a few weeks, infected T helper cells are recognised and then destroyed by T killer cells
  • This greatly reduces the rate of virus replication, but doesn't completely inhibit it
  • It also however weakens your immune system
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The Chronic Phase (Latent Phase)

  • The virus continues to reproduce rapidly but numbers are kept in check by immune system
  • May be no symptoms during this phase, but there can be an increasing tendency to suffer colds or other infections, which take longer than usual to go away
  • Dormant diseases such as TB and shingles and reactivate
  • Chronic phase can last many years, especially in healthy young people, who have healthy lifestyles and are getting drug treatment
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The Disease Phase

  • The increased viral load and declining number of T helper cells indicated the onset of AIDS
  • During this phase, the decrease in number of T helper cells leaves the immune system extremely vunerable to other diseases
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  • No treatment to get rid of HIV
  • Drugs available to restrict production of more viruses
    • known as antiretroviral
  • Two main types:
    • Reverse transcriptase inhibitors- prevent the viral RNA from making DNA for integration into the host's genome
    • Protease inhibitors- which inhibit the proteases that catalyse the cutting of larger proteins into small polypeptides for use in the contruction of new viruses
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