Acquired Immune Deficiency Syndrome (AIDS) is caused by the human immunodeficiency virus (HIV). Often, HIV doesn't initially cause AIDS. HIV causes AIDS by wearing down victims' immune systems until they can no longer fight off other infections and diseases. Normally, the human immune system fights opportunistic infections, but in AIDS patients, these conditions can be life-threatening and require medical intervention. It's the appearance of these opportunistic diseases that indicates that a patient has developed AIDS.
The virus that causes AIDS may have its origins in a similar virus that attacked primates in Africa. According to expert opinion, humans then became infected with the virus when they hunted these primates for food and came into contact with their infected blood during butchering or cooking. The virus then may have evolved into the form of HIV that causes AIDS today.
The modern HIV virus attacks the immune system by killing a certain type of white blood cell called CD4 cells. These white blood cells are crucial for protecting the body from viruses, bacteria. As the HIV destroys more and more CD4 cells, the victims' immune system becomes weaker and weaker. It can take many years, however, before enough blood cells are destroyed and HIV causes AIDS.
To diagnose AIDS, medical professionals look at the CD4 count and other complicating factors. A patient's CD4 count must be under 200 for a diagnosis AIDS. AIDS-defining complications are also considered. These opportunistic infections include a specific type of pneumonia, toxoplasmosis, cytomegalovirus, tuberculosis and cryptosporidiosis.
Before HIV attacks the immune system and causes AIDS, of course, the virus must enter the body and the bloodstream. This can happen in only a few ways. One of the primary ways for HIV to enter the body is through sexual contact. The virus is present in blood, vaginal fluids, and semen. During oral, vaginal or anal sex with an infected partner, these fluids can enter the uninfected partner's body through open sores and tears.
HIV can also enter the body in three other instances. The first is a blood transfusion, although this is less frequent now that many blood banks and hospitals around the world screen donated blood for the virus. Another way that people can become infected is by sharing needles, as is often the case with intravenous drug users. A baby can contract HIV from his or her infected mother either in the womb or during birth. An infant can also contract HIV from his or her mother through breastfeeding.