HIV is the virus that may causes AIDS. HIV belongs to a subset of viruses called retroviruses or slow virus.
This is because it is a progressive disease. HIV is entered through the body through the mucous membranes or thru blood to blood contact.
Once you get the virus it slowly begins to attack the immune system, killing off healthy immune system cells. The deterioration and destruction of immune function leads to AIDS.
AIDS is the final stage of the HIV infection. A person is said to have AIDS when the cd4 counts drops below 200 and or a person has 1 or more opportunistic infections. The OIs, as they are called, are normal infections that a healthy person would be able to fight off.
The four stages of the HIV infection are as follows:
1) The period following infection is called the window. It is called this because it reflect the window of time between infection and that which antibodies are develop in a person. The HIV test looks for antibodies not the virus.
2) The second stage is called seroconversion. This is when the body begins to develop lots of antibodies to fight off the virus in the body. During this period a person may have flu like symptom. Also during this period is said to be very infectious.
3) The third stage is called symptom free. During this period a person may have no symptom what so ever. This can last any where from 6 months to well over ten years. The medical world is not sure why some people are living symptom free for so long.
4) The final stage is called AIDS. This is the period when TCELL drop to below 200 and the OI"S are present.
So, as we see, HIV is a infection that will leads to AIDS.