HIV stands for the Human Immunodeficiency Virus. The main way in which HIV is passed on is through unprotected sex. It can also be passed on through sharing injection needles or blood transfusions. Babies can also contract HIV from HIV positive mothers during pregnancy, birth and breastfeeding. However if mothers stick to the Prevention of Mother-to-Child Transmission (PMTCT) programmes they have only a very small chance of passing the virus on to their baby (less than 5 percent). This involves being on antiretroviral therapy (ART), the medicine that is used to treat HIV.

What are CD4 cells?

CD4 cells are white blood cells in the immune system that fight off infection. They are sometimes called T4-cells or helper cells. Their job is to send a message to the CD8 'soldier' cells in the immune system, to tell them to attack the virus. A CD4 count is a measure of how many CD4 cells there are in a small sample of blood. A normal CD4 count is between 800 and 1200. A low CD4 count means that you have a weak  immune system.

How HIV affects the body

The immune system is the body's defence force. It protects the body against disease. HIV is a virus that attacks and weakens the immune system. It does this by hijacking the immune system's CD4 cells. It attaches itself to these 'good cells' and becomes part of the cell. The virus turns these cells into factories to make more copies of HIV. In the process of making more HIV, the CD4 cells are destroyed. This means that as more and more HIV is made, more and more CD4 cells are destroyed. This is why when someone has HIV, and they are not taking antiretroviral drugs (ARVs), the amount of HIV in their blood and body goes up (their viral load) as their CD4 count drops. When the CD4 count is low and the immune system is weakened, the body can't fight diseases, such as TB.

What is viral load?

Viral load is used to describe how much of th HIV virus there is in a person's blood. If a person is on antiretroviral treatment (ART) their viral load will get less and less. It will be supressed. Eventually the virus will not show up in blood test. Usually this means that their CD4 count will go up and they will be heialthier.

Are HIV and AIDS the same thing?

No, HIV is a virus that causes infection. AIDS, which stands for acquired immunodeficiency syndrome, is a condition that develops when a person does not take HIV medication. It is the last stage of the HIV infection. A person's CD4 count drops to below 200 and their immune system is weakened so much that they will easily get an AIDS-related illnesses. AIDS is the last stage of the HIV infection. Without treatment HIV advances to AIDS.