HIV/AIDS is an infectious disease. The letters stand for Human Immunodeficiency Virus, which is the name of the organism that causes this disease, and Acquired Immune Deficiency Syndrome, which is the name of the set of symptoms that characterize this condition.

AIDS was first recognized as a new disease in 1981, when a number of young gay men in New York and Los Angeles were diagnosed with symptoms not usually seen in individuals with healthy immune systems. This information was reported to the Centers for Disease Control and Prevention (CDC), the branch of the U.S. government that monitors and tries to control disease outbreaks.

Many new cases were soon discovered of what appeared to be a disease associated with the breakdown of the body's immune or natural defense system.

Normally, the immune system, which consists of a wide array of cells that can identify and eliminate invading bacteria, fungus, viruses and other disease-causing pathogens, is able to protect us from harm. One part of the immune response involves the creation of antibodies, which are chemical substances that fight against infectious agents.

HIV/AIDS — "Opportunistic" Infections
If there is damage to our immune system, however, antibodies and other bodily defenses may not be produced and we are subject to many different infectious diseases, including those called "opportunistic infections" that are usually only able to strike when the body's defenses are weakened.

Although the first cases of the disease that came to be called AIDS were among homosexual men, within a few months the same strange set of symptoms was being seen in female patients and hemophiliacs, and before long injection drug users and their non-drug using sex partners and children also were being diagnosed with AIDS. It became clear to the CDC that we were facing a significant new epidemic.

AIDS — A Worldwide Health Threat
Before long, it was recognized that AIDS should be labeled a pandemic because it was not limited to a certain region or country but was truly a worldwide health threat of massive proportions. Since the beginning of the pandemic, several million people around the world have died of AIDS.

Since its discovery, scientists immediately began trying to find the cause of AIDS and to understand how it so severely damages the human immune system. By 1983, French and American teams lead by Dr. Luc Montagnier and Robert Gallo developed a blood test to detect exposure to HIV.

People who have been exposed to the virus, which means that it is in their bodies, are said to be HIV positive, while those who have not been exposed are HIV negative. This is what the standard HIV blood test (or antibody test) reveals. The test tells whether or not your body has begun creating antibodies targeted to fighting HIV. Unfortunately, while the body mounts a strong defense against HIV, it appears that in most cases the body alone cannot successfully defeat the virus.

It is now known that after HIV has entered a person's body, he/she can live for a number of years without having any noticeable symptoms. Individuals in this stage of the disease have HIV infection but not AIDS per se.

AIDS-Related Infections Are Growing
Once an infected individual begins to develop the set of opportunistic infections associated with immune system damage, they are defined medically as having AIDS. In recent years, the number of opportunistic infections known to be associated with AIDS has grown.

Currently, 26 different clinical conditions are used in defining whether or not a person has developed AIDS. Also, as scientists came to recognize how HIV affects the human body, an additional defining feature of AIDS based on the health of the person's immune system was added to a physician's diagnostic guide.