It has spread to 70 million people, killed 30 million and an estimated 40 million more will be infected over the next decade. Where did it come from? How do we treat it? Why can't we stop it?
The Immune System
HIV is unique because it attacks the very heart of the immune system, the CD4 cell, thus disrupting the body's entire immune response. Here's an overview of how the human immune system works and the crucial role of the CD4 cell.
The Human Immunodeficiency Virus
How do you get it and how does it destroy the body? At what point is an HIV-infected person medically diagnosed as having AIDS? Why are some people immune to HIV? Why do some people never progress from HIV to AIDS?
How do physicians combat HIV? What is a typical treatment regimen like, and what are the side effects? Why aren't the drugs a cure?
Is an AIDS Vaccine Out of Reach?
After HIV was discovered in 1984, public health officials estimated a vaccine would be ready within two years. Why has it proven so difficult?
How It All Began: HIV Before the Age of AIDS
In May 2006, scientists determined the specific chimpanzee family that harbored the virus that has caused 90 percent of mankind's HIV infections. Here's details on this latest research into where HIV began and how it crossed the species barrier.
Viruses and Humankind
Joshua Lederberg, a Nobel Prize-winning scientist for his work in bacterial genetics, warns against complacency in the age-old contest between mankind and microbes -- viruses and bacteria. He lays out why our "only real competitors remain the viruses."