Zimbabwe nurse and health worker. Image credit icrc.org

Zimbabwe nurse and health worker. Image credit icrc.org

ZIMSEC O Level Combined Science Notes: Disease:Immunity and Immunisation

HIV and Its effects

  • HIV stands for Human Immunodeficiency Virus
  • It lives in the body fluids including blood, saliva, semen, tears etc
  • It enters the body in the following ways:
    1. during unprotected sex with an infected person
    2. through sharing contaminated (by HIV) needles when administering drugs
    3. during blood transfusion if the blood is contaminated by the virus
    4. from infected mother to child during pregnancy, at birth and during breastfeeding
  • The virus reduces the body’s ability to fight infection and disease by destroying the body’s white blood cells responsible for producing the antibodies
  • A person is deemed to be HIV positive if that person’s blood is tested for the HIV virus and it is found to be present in his/her blood
  • A person can look healthy and yet be HIV positive


  • Stands for Acquired Immuno Deficiency Syndrome
  • It is a stage during the HIV infection when the HIV has destroyed the body’s defence ystem, causing the individual to become susceptible (vulnerable) to ┬ámultiple infections and failing to recover
  • This stage can (and will likely) lead to death
  • There is no cure for AIDS
  • Exercising a healthy diet, maintaining a positive attitude, seeking early treatment when an opportunistic infection surfaces and
  • Taking Antiretroviral drugs (ARVs)
  • All significantly prolong a person’s life

To access more topics go to the Combined Science Notes page