HIV and AIDS Introduction

The primary cause of AIDS is infection with the human immunodeficiency virus (HIV). People infected with HIV range from those that may have a positive test for HIV but exhibit no symptoms for many years (asymptomatic), to individuals who have a late stage HIV infection. Those in the later stages of infection have progressive HIV coupled with an AIDS-defining illness, such as, Pneumocystis carinii pneumonia or Kaposi’s sarcoma.

HIV is a viral infection that infects CD4 lymphocytes, a type of white blood cell responsible for coordinating the functions of the immune system to fight infection. HIV reproduces rapidly in the infected cells and destroys them. If the HIV infection is left untreated, the number of CD4 lymphocytes begins to fall, causing eventual destruction of the immune system.

Diagnosis of AIDS can be made with a positive HIV test and a CD4 count of less than 200 cells per microliter of blood (individual cases may vary). HIV is not contagious and cannot be transmitted by ordinary human contact. HIV is carried in body fluids including; blood, semen, vaginal secretions, salvia and breast milk. It is most commonly transmitted by sexual interaction, sharing or reusing needles contaminated with the virus, infected mother to fetus, and from organ transplants or blood transfusions. Organs, tissues, and blood donors are now routinely screened for HIV.