In 1999, scientists discovered the origins of HIV-1. HIV has been found to be related to a strain of Simian Immunodeficiency Virus (SIV) found in a subspecies of chimpanzees native to west equatorial Africa. Scientists believe that HIV was introduced into the human population when hunters became exposed to infected blood.
The Centers for Disease Control and Prevention (CDC) is sure that the virus existed in the United States since at least the mid- to late 1970s. From 1979-1981 rare types of pneumonia, cancer and other illness were recognized by doctors around the United States. In 1982, public health officials termed the occurrences of rare illnesses Acquired Immune Deficiency Syndrome (AIDS). In 1983, scientists discovered the virus that causes AIDS, which was later named Human Immunodeficiency Virus (HIV).