HIV is a kind of virus that destroys the immune system gradually. This virus affects a type of white blood cell called the T lymphocyte or T cell in the blood. As we know that white blood cells function as fighter cells that helps the body fight off all kinds of germs and diseases. People who have been tested and found to have several symptoms of HIV or human immunodeficiency virus in their blood are diagnosed as having HIV positive.
People with HIV positive certainly have HIV virus in their blood. HIV virus may take a long period of time to damage immune system for that person to get sick and develop AIDS. The HIV virus is silently reproducing itself and destroying T cells although the HIV positive person may feel fine. This is very dangerous because we can not distinguish HIV positive person with other health person. The HIV positive person is still contagious during this time which means they can infect others too.
People with HIV positive can no longer fight off infections when HIV virus has destroyed most of white blood cells. They get very sick when the person's immune system has weakened. When the person has a very low number of T cells and shows several signs of a serious infection, a doctor can diagnose them get infected by AIDS.
Most people do not feel any change in their body after they are get infected by HIV virus. That is why people with HIV virus do not show any symptoms of HIV-AIDS for years. Some people develop common illness like flu, cold or fever for a few days to a few weeks after being infected but these symptoms of HIV usually go away after several days. The person with symptoms of HIV might begin to have swollen lymph nodes, weight loss, infections in the mouth, diarrhea, or they might feel tired and weakness all of the time.
More information about HIV, you can read in HIV seroconversion : http://www.djamilah-najmuddin.com/bukti-hasil-laboratorium-pasien