AIDS (ACQUIRED IMMUNODEFICIENCY SYNDROME)

HIV

The disease known as AIDS is a complicated illness that may involve several phases. It is caused by a virus that can be passed from person to person. AIDS impairs the human body's immune system the system responsible for warding off disease and leaves the victim susceptible to various infections.

AIDS was first conclusively identified in the United States in 1981, when 189 cases were reported to the Centers for Disease Control. Within a decade the disease had spread to virtually all populated areas of the world. In the United States alone there are about 65,000 new cases every year. The origin of the AIDS virus is uncertain, but it may have originated in Central Africa.

The first AIDS patients in the Americas and Europe were almost exclusively male homosexuals. Later patients included those who used unsterilised intravenous needles to inject illicit drugs; haemophiliacs (persons with a blood-clotting disorder) and others who had received blood transfusions; females whose male sexual partners had AIDS; and the children of such couples. However, since 1989, heterosexual sex was found to be the fastest growing means of transmission of the virus, with 90 percent of new cases originating from heterosexual sex.

Public awareness of the disease gradually built up as high-profile victims began to die: actor Rock Hudson (1985), clothes designer Perry Ellis (1986), choreographer Michael Bennett (1987), photographer Robert Mapplethorpe (1989), and Oscar-winning director Tony Richardson (1991). When basketball superstar Magic Johnson announced in 1991 that he had contracted the AIDS virus, the feeling spread quickly that anyone, not just particular groups of people, could be at risk. This was again confirmed as tennis legend Arthur Ashe announced in 1992 that he had been infected with the virus for several years.

The AIDS virus. American researchers initially named the virus that causes AIDS the human T-lymphotropic virus, type III or HTLV-III. After researchers discovered in the late 1980s that there were several forms of the AIDS virus, the original virus was renamed the human immunodeficiency virus type 1, or HIV-1.

The virus enters the bloodstream and destroys certain white blood cells, called T lymphocytes, that play a key role in the functioning of the immune system. The virus can also infect other types of cells in the body, including the immune-system cells known as macrophages. Unlike T lymphocytes, however, macrophages are not killed by the virus. In fact, research has suggested that macrophages may carry the AIDS virus to healthy brain cells, to the lymphatic system, and to other healthy cells in the body.

What happens after infection. Most people recently infected by the AIDS virus look and feel healthy. In some people the virus may remain inactive, and these people act as carriers, remaining apparently healthy but still able to infect others. After a few years, some people may develop AIDS-related complex, or ARC. Its symptoms may include fever, fatigue, weight loss, skin rashes, a fungal infection of the mouth known as thrush, lack of resistance to infection, and swollen lymph nodes. Sometimes the symptoms of ARC disappear, but the condition frequently goes on to become AIDS. Though it can take up to 20 years after the virus is contracted for AIDS to fully manifest itself, the average time is one to two years.

The AIDS virus causes so much damage to the immune system that the body becomes susceptible to a variety of opportunistic infections infections that are less harmful to people with normal immune systems but take advantage of the breakdown in an AIDS sufferer's immune system to produce devastating and eventually lethal diseases. Among the most frequently occurring opportunistic infections are tuberculosis and a type of pneumonia caused by the micro-organism Pneumocystis carinii. AIDS sufferers are also more likely to develop certain tumours, particularly Kaposi's sarcoma, a rare form of cancer. The AIDS virus may also attack the nervous system and cause brain and eye damage. The average life expectancy for an AIDS victim from the onset of symptoms is one to five years.

How AIDS is spread. AIDS is transmitted by direct contamination of the bloodstream with body fluids that contain the AIDS virus, particularly blood and semen from an HIV-infected person. The virus is usually transmitted through various forms of sexual intercourse, the transfusion of virus-contaminated blood, or the sharing of HIV-contaminated intravenous needles.

The AIDS virus cannot penetrate intact bodily surfaces, such as skin, and quickly perishes outside the human body. Consequently, AIDS is not spread by casual physical contact or by sneezing. The virus has been found in tears and saliva, but it exists there in such low concentrations that transmission from these body fluids is extremely rare. There are no known cases of AIDS transmission by insects such as mosquitoes or by domestic animals. Studies show that the virus is usually passed to an infant close to or during delivery, rather than moving across the placenta during pregnancy. Recently infected mothers can transmit the virus to their children via breast milk. The United States Congress approved guidelines recommending that health care workers who perform invasive procedures be tested for the AIDS virus but the testing and disclosure of results would be voluntary; no restrictions would be placed on those who tested positive.

There are several ways to reduce the spread of AIDS through sexual contact. These include practising abstinence no intercourse or practising safe sex. Practising safe sex means either participating only in a monogamous, or mutually exclusive, relationship in which both people are free of HIV infection, or using latex condoms whenever engaging in intercourse.

Detection and treatment. Usually, when the AIDS virus enters the bloodstream, the body's immune system produces antibodies to battle the micro-organism Blood tests can detect these antibodies and therefore can indicate exposure to the virus. However, these tests occasionally give false readings and only begin to give accurate results within two weeks to three months after infection, during which time an infected person may pass the virus to others. Scientists do not know exactly how the AIDS virus damages the immune system, nor do they understand why the natural antibodies developed to destroy the virus are ineffective.

By 1987 the drug azidothymidine (AZT) had proved effective in slowing the reproduction of the HIV-1 virus in humans, but it is highly toxic and cannot be taken by many patients. In 1989 researchers determined that lower doses of AZT would be effective and less harmful for patients that have early symptoms of AIDS and for children with AIDS.

Dideoxyinosine (DDI) was approved in the United States in 1991 for the treatment of HIV infection. This drug is a useful replacement for AZT and is used in children and other patients for whom AZT is too toxic. In 1992 zalcitabine, or DDC, became the third drug approved to treat people infected with the AIDS virus. It was, however, approved for use only in combination with AZT to treat adults with advanced HIV infection.

Several other drugs and treatments have recently been approved or become available experimentally for the treatment of P. carinii pneumonia, Kaposi's sarcoma, and other AIDS-related conditions. Several vaccines against AIDS are being developed and tested.

BIBLIOGRAPHY FOR AIDS

Cozic, C.P., and Swisher, Karin, eds. The AIDS Crisis (Greenhaven, 1991).

Hein, Karen, and others. AIDS: Trading Fears for Facts, updated ed. (Consumer Reports Books, 1991).

Tiffany, Jennifer, and others. Talking with Kids About AIDS (Parent AIDS, 1993).