HIV & AIDS (DP IB Biology)

Transmission of HIV

• Human Immunodeficiency Virus is a retrovirus

• The virus is unable to survive outside of the human body; it needs host cells in order to replicate

• HIV is not transmitted by a vector (unlike in malaria), it is spread by direct exchange of body fluids

• This means HIV can be transmitted in the following ways:

  • Sexual intercourse

  • Blood donation

  • Sharing of needles used by intravenous drug users

  • From mother to child across the placenta

  • Mixing of blood between mother and child during birth

  • From mother to child through breast milk

HIV Infection

• HIV is made up of several key components including RNA and the enzyme, reverse transcriptase, which is used to produce DNA in the host cell; this classifies HIV as a retrovirus

• HIV infects the body and attacks a type of lymphocyte cell called a T-helper cell

• T-helper cells are a key component in the production of antibodies, so HIV inhibits the body's capacity to produce antibodies

• In the early stages of infection, antibodies are produced to fight HIV, these can be detected in blood tests

  • The individual is said to be HIV positive 

The development of AIDS

• As the infection progresses, the ability to produce antibodies significantly reduces

• This renders the immune system unable to fight off other pathogens and so the individual becomes prone to infection from other opportunistic pathogens

• When the individual is suffering from several diseases or conditions at the same time, they are said to have acquired immune deficiency syndrome (AIDS)

• Progression of HIV, from the initial infection to the development of AIDS, can be slowed down using anti-retroviral drugs

  • Due to highly successful drugs, many HIV positive individuals are able to live full-quality lives with normal life expectancies