In the 1970s many scientists assumed that infectious disease were no longer a major threat in developed countries, since they felt that they were winning the battle against polio, classify term="smallpox" project="wsd/wi" type="bookxref">smallpox, and other serious infectious diseases. Many researchers began to focus on developing cures for non-infectious conditions such as cancer and heart disease. Their confidence was shattered in early 1981 by the advent of AIDS--Acquired Immune Deficiency Syndrome--a deadly infectious disease that suppresses the immune system, and was caused by Human Immune Deficiency Virus (HIV), part of a group of viruses known as retroviruses. The name AIDS was coined in 1982, and patients with AIDS die from opportunistic infections because HIV cripples the immune system. Opportunistic diseases have the opportunity to take hold because the immune system is severely impaired.

Following the discovery of AIDS, scientists tried to identify the virus that causes...