HIV Transmission

The Biological Basics

The Biology Bit

Human Immunodeficiency Virus (HIV) is an incurable disease that attacks the immune system in the body. The virus can cause a life threatening condition called AIDS (Acquired Immunodeficiency Disease). HIV is incurable but many people live full and active lives with the help of drug regimes.

HIV is a virus. Virus’s are incredibly small, yet incredibly complex. The virus needs a host to reproduce and once inside the host it can start to make copies of itself. As it does this it damages the host and the host becomes ill. The host for HIV is the Human Immune System. HIV attacks the cells that are designed to get rid of virus’s and disease. That is why HIV is such a dangerous virus. The immune system is made up of white blood cells (also call lymphocytes). These white blood cells find virus’s in the body, identify them and produce a special protein called an antibody which stick to virus’s and stop them infecting cells. The antibodies also attract ‘killer’ immune cells, which destroy the virus.

HIV infects a particular type of white blood cell called the Helper T Cell or CD4 cell. This cell’s job is to identify infection and stimulate antibody production. By attaching to the Helper T cells HIV makes the immune system work in a different way. The virus uses the Helper T cell for replication and instead of fighting the virus they spread it. In effect the T cells become HIV factories which weaken and eventually destroy the cells. Eventually the body is unable to fight infections in the body.

The diagram below shows how HIV copies itself in more detail.


HIV copying illustration

The Transmission Bit

For HIV transmission to occur three things need to be in place, these are:

  1. There has to be a sufficient amount of virus present. (Quantity) This means that there has to be at least some virus present. This is why you cannot transmit HIV through saliva or tears, because there is not enough (Quantity) of the virus.

  2. The virus has to get into the body of an un-infected person through an effective route of transmission. (Route and Susceptibility). This is easily explained if you think about the skin, this skin is a great barrier to transmission because the virus cannot get through this unless there is a cut or wound, this makes the transmission route easier. If the skin is pierced for example by a needle then this makes the route of transmission easier , or more susceptible.

  3. The HIV virus has to be of sufficient quality. (Quality). This means that is has to be strong enough. There is no way to tell how strong your virus is, even if you have an undetectable viral load you may still have a virus that is of good quality.