Acquired Immune Deficiency Syndrome (AIDS)

Acquired immune deficiency syndrome (AIDS) is a progressive, degenerative disease that affects several major organ systems, including the immune system and central nervous system. It is associated with human immunodeficiency virus (HIV), a viral infection that progressively weakens the immune system.

AIDS is the final stage of infection with HIV. Not everyone infected with the virus gets AIDS, but when a person has AIDS it generally means that a number of different diseases and conditions are present. The Centers for Disease Control's diagnostic criteria for AIDS say that a person who is infected with HIV has a severely compromised immune system or has become ill with an opportunistic infection. When the patient's blood test shows a CD4 count of less than 200 cells per cubic ml of blood, it indicates progression to AIDS, or stage 3 of HIV infection. The CD4 cell is a T-cell (CD4 T lymphocyte), a white blood cell that helps a healthy body fight infection. HIV attacks CD4 cells.

AIDS was first recognized in 1981 as a cluster of symptoms in homosexual men in New York City and San Francisco. Eventually, similar symptoms were found among intravenous drug users, people with hemophilia, and other recipients of blood transfusions. In 1984, HIV was isolated and subsequently determined as the probable cause of AIDS.

HIV is transmitted through sexual intercourse, contact with infected blood and blood products, and the birth process. However, casual social contact—even if close and prolonged—has not been found to spread HIV. The greatest number of HIV cases are sexually transmitted, through both homosexual and heterosexual intercourse. Screening of donated blood and blood products since 1985 has drastically reduced the risk of transfusion-related HIV. Children may be infected in utero or by exposure to blood and vaginal secretions during childbirth. The child of an infected mother can become infected, but if the mother properly takes antiretroviral medication during pregnancy, the risk of her newborn being infected is only about 1%.

Persons infected with HIV initially show no symptoms. Within three to six weeks after infection they may exhibit flu-like symptoms that last up to three weeks and resolve spontaneously. In the past, nearly everyone infected with HIV eventually reached the stage of AIDS. But today, because of improved treatment, most people positive for HIV do not develop AIDS. A person who does reach the late stage of infection, or who has AIDS, becomes vulnerable to opportunistic infections and diseases that take advantage of reduced immune system defenses. These include Candidiasis, pneumocystis carinii pneumonia (PCP), herpes and other viral infections, toxoplasmosis, and tuberculosis. AIDS also weakens the body's defenses against certain cancers, and conditions such as lymphoma and Kaposi's sarcoma are common complications of the disease. AIDS also attacks the nervous system. Neurological disorders such as encephalitis and dementia can occur in people who have AIDS. HIV/AIDS patients are also prone to blood abnormalities, respiratory infections, and gastrointestinal problems, including diarrhea, which is partly responsible for the weight loss that occurs in the course of the disease.

People who have HIV/AIDS may have an increased risk for developing mood disorders, anxiety disorders, or cognitive disorders. AIDS is a chronic and potentially terminal illness, and those who have it must care for themselves and take regular medication. AIDS still can be associated with negative reactions or even discrimination from people who do not understand the disease and how it is spread. Further, the person who has HIV infection faces the stress of revealing to others his or her HIV-positive status. The isolation and lack of social support for some people who have AIDS can add to stress or depression. People who have HIV may worry that they will eventually succumb to AIDS, and then must face the physical changes associated with the disease. Anyone diagnosed with AIDS should discuss possible mental health services with their physician.

According to the World Health Organization, an estimated 35 million people around the world were living with HIV in 2013. The highest incidence of AIDS is in major cities in Asia, Africa, and the United States. In the United States alone, more than 1.2 million people were living with HIV infection in 2013, and about 26,600 new cases of AIDS were diagnosed in 2013. About 13,700 people died in 2012 who had AIDS.

HIV is usually diagnosed through a test called ELISA (enzyme-linked immunosorbent assay), which screens the blood for HIV antibodies. If the test is positive, a more specific test, the Western blot assay, is administered. Most patients will test positive for HIV one to three months after being infected, and 95% will test positive after five months. There is no effective vaccine against the HIV virus, and no known cure for AIDS, but antiretroviral drugs have been effective in slowing the progression of the disease, particularly in slowing the suppression of the immune system.

The best method of containing the AIDS epidemic is education and prevention. Much of the anti-AIDS effort both in the United States and globally has been directed toward promoting safer sex practices, including abstinence (especially among young people) and the use of latex condoms, which greatly reduce the chance of infection. The threat of HIV among intravenous drug users has been addressed by programs offering education, rehabilitation, and the free distribution of sterile needles. Modification of sexual behavior among homosexuals has been successful in reducing the incidence of new HIV infections among men having sex with men.


Antiretrovial medications—
Drugs used against retroviruses, such as HIV.Themedicationscan'tcureHIV, but can help prevent the virus from growing further.
Immune system—
The body's organs and processes that help protect against diseases and infections.
Opportunistic infection—
Certain infections that can occur more easily or more often in people who have weak immune systems.
A disease caused by infection with a parasite.



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