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.

"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.

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.

Prior to the discovery of new treatments for AIDS, most people who were infected with HIV eventually developed full blown AIDS and most of these individuals died of this disease. However, there are some strains of HIV that are not as lethal as others, and scientists are attempting to understand variation in the virus and the ability of the immune system to respond to viral infection.

As the name HIV implies, the disease is known to be caused by a specific virus. Viruses are a curious type of phenomenon. In a sense, they are only partial organisms in that they must live inside another organism or host. Otherwise they are dormant. Moreover, their entire existence is focused on spreading from one host to another and on reproducing themselves.

What Happens in the Body
When HIV enters a human body, it tends to seek out and attack a particular group of white blood cells commonly known as the T-helper cells. These cells are part of the body's immune system.

When the body is invaded by a pathogen, there is a rapid increase in the production of T4 cells, which is the body's signal that a pathogen is present and an immune response must be mounted for protection. Unfortunately, HIV interferes with this process.

When HIV encounters a T4 inside the blood system, it attaches itself and inserts its genetic code into the T4. In this way, the T4 is transformed into a biological factory that begins producing new HIV.

Ultimately, the T4 cell bursts, releasing new virus into the blood stream, and these, in turn, seek out other T4 cells to invade. In the process of its own reproduction, HIV destroys the ability of the body to fight infection, leading to illness and possible death.

HIV/AIDS has generated a considerable amount of controversy. Because the disease was first diagnosed in homosexual patients, some people assumed that it was somehow a peculiarly homosexual disease, perhaps a consequence of sexual or other practices common among homosexual men. This proved to be quite inaccurate. HIV is a blood-borne disease, meaning that the natural environment of the virus is human blood. Any behaviors that result in blood and other body fluids like semen or breast milk passing from one person to another can transmit the virus between people.

How AIDS Is Transmitted
Most homosexual men with HIV became infected through sexual contact with other men, but there is nothing specifically "homosexual" about HIV/AIDS. Many men and women around the world have been infected with HIV through heterosexual contact. It appears that some factors, such as having another sexually transmitted disease like syphilis, or engaging in sexual practices that tear the skin lining of participants' sexual organs, may significantly facilitate infection occurring during sex.

Another common way HIV is transmitted is through injection drug use, specifically the sharing or reuse of hypodermic syringes or other injection paraphernalia. When drug users inject, their blood often enters the syringe. If they are infected with HIV, and should someone use this syringe after them, the virus may be transmitted via the syringe from the first to the second syringe user.

Other equipment used to inject illicit drugs, such as the "cooker" (usually a bottle cap or half of a soda can) in which drugs and water are mixed, may also serve as a route of HIV transmission when people "shoot up" drugs together.

One method for limiting HIV transmission is syringe exchange, which involves providing drug users with sterile syringes in exchange for their used ones. While there is considerable research data showing that syringe exchange is effective in limiting the spread of AIDS among drug users, some people feel very uncomfortable with providing drug users with syringes.

The public health debate over syringe exchange is ongoing. Additionally, there has been controversy over the ability of HIV/AIDS to be transmitted through casual contact, such as shaking hands.

Casual Contact Not a Culprit
Further, some people have feared that mosquitoes or other biting insects might transmit HIV. Considerable scientific research has shown that HIV/AIDS is not transmitted through casual contact unless blood from one person passes into the body of the other.

Likewise, hugging, shaking hands with, or even sharing eating utensils with a person infected with HIV is not a risk for HIV infection, nor can biting insects transmit the virus.

Finally, HIV is not and never has been transmitted by donating blood. Prior to the treatment of the blood supply, it was possible to become infected through receiving a blood transfusion, but controls on blood banks in the U.S. have all but eliminated this risk.

While HIV/AIDS is a significant health risk, it is possible to protect yourself from becoming infected. Proper use of latex condoms during oral, anal, or vaginal sex, is the most effective way to avoid possible infection for those who are sexually active.

Abstinence from sex is another approach, although it is not one that many adults choose. When having sex, it is important to accept that you cannot tell by looking whether someone is infected with HIV/AIDS. AIDS does not discriminate. It will infect rich and poor people, people of all races and nationalities, gay and straight people, men and women, adults and children.

A Tie That Binds
AIDS binds us all together in a common community of risk, and demands that we all exercise appropriate health precautions like condom use. For couples who are attempting to have a child (and hence desire not to use a condom), HIV testing can suggest with reasonable certainty whether you and your partner have been infected.

Couples and individuals can use test results in making decisions about proceeding or not with forgoing condom use for the purposes of conceiving a child.

While transmission of HIV from an infected mother to her unborn child was common earlier in the epidemic, drugs like AZT have significantly lowered this form of HIV transmission.

Additionally, a variety of new drugs and drug combinations have become available in recent years. Some of these drugs are very effective in treating the opportunistic infections that are caused by HIV disease.

Others, like the protease inhibitors, are effective in interfering with reproduction of the virus and limiting the "viral load" or quantity of virus in an infected person's body. These new drugs have allowed many infected individuals to lead longer, healthier, more active and productive lives.

Currently, there is no vaccine to prevent HIV infection and there is no cure.