AIDS Health Article

Definition

Acquired immunodeficiency syndrome (AIDS) is the final and most serious stage of the disease caused by the human immunodeficiency virus. Symptoms begin when an HIV-positive person presents a CD4-cell (also called T cell, a type of immune cell) count below 200. AIDS happens concurrently with numerous opportunistic infections and tumors that are normally associated with the HIV infection.

The most common neurological complications of AIDS involve opportunistic infections of the brain such as progressive multifocal leucoencephalopathy (PML) and meningitis, other opportunistic infections such as herpes zoster (shingles), peripheral neuropathy, depression, and AIDS-related dementia.

Description

AIDS was first recognized in 1981 and has since become a major worldwide pandemic. Abundant evidence indicates that the human immunodeficiency virus (HIV), discovered in 1983, causes AIDS. By leading to the destruction and/or functional impairment of immune cells, notably CD4+ T cells, HIV progressively destroys the body's ability to fight infections and to resist certain cancer formation.

Before the HIV infection became widespread in the human population, AIDS-like syndromes occurred extremely rarely, and almost exclusively in individuals with known causes of immune suppression, such as those receiving chemotherapy or those with underlying cancers. A marked increase in unusual infections and tumors characteristic of severe immune suppression was first recognized in the early 1980s in homosexual men who had been otherwise healthy and had no recognized cause for immune suppression. An infectious cause of AIDS was suggested by geographic clustering of cases, a sexual link among cases, mother-to-infant transmission, and transmission by blood transfusion.

Isolation of the HIV from patients with AIDS strongly suggested that this virus was the cause of AIDS. Since the early 1980s, HIV and AIDS have been repeatedly associated; the appearance of HIV in the blood supply has preceded or coincided with the occurrence of AIDS cases in every country and region where AIDS has been noted. Individuals of all ages from many risk groups, including homosexual men, infants born to HIV-infected mothers, heterosexual women and men, hemophiliacs, recipients of blood and blood products, health care workers and others occupationally exposed to HIV-tainted blood, and injection drug users have all developed AIDS with only one common denominator: HIV.

HIV destroys CD4+ T cells, which are crucial to the normal function of the human immune system. In fact, depletion of CD4+ T cells in HIV-infected individuals is an extremely powerful predictor of the development of AIDS. Studies of thousands of individuals have revealed that most HIV-infected people carry the virus for years before enough damage is done to the immune system for AIDS to develop; however, with time, a near-perfect correlation has been found between infection and the subsequent development of AIDS.

Demographics

In the United States, more than 733,000 people have AIDS, and an estimated one to two million people have HIV infection without the symptoms of AIDS.

Internationally, since the AIDS epidemic began, more than 16 million deaths have been attributed to AIDS. The current estimate of worldwide disease prevalence is more than 33 million HIV infections. Ninety-five percent of these cases are in developing countries, generally in sub-Saharan Africa and Southeast Asia.

Most HIV infections still occur in men; however, the frequency of infection in women is increasing, especially in developing countries. In the United States, fewer than 16% of all HIV cases are in women, whereas worldwide an estimated 46% of all HIV patients are women.

Causes and symptoms

The cause of primary AIDS is infection with the HIV virus, transmitted via infected blood or body fluids. Methods of transmission of the virus include unprotected sex, especially anal intercourse; occupational needle stick or body fluid splash, which has an estimated transmission rate of less than 0.3%; sharing of needles in drug abuse; and receiving contaminated blood products.

Opportunistic infections occur in individuals whose CD4 count is less than 200 cells/mm³ and those not taking preventative drugs.

Symptoms of AIDS include:

• cough and shortness of breath
• seizures and lack of coordination
• difficult or painful swallowing
• confusion and forgetfulness
• severe and persistent diarrhea
• fever
• vision loss
• nausea, abdominal cramps, and vomiting
• weight loss and extreme fatigue
• severe headaches with neck stiffness