"Teenage Problems"
What Is AIDS?
Defining a Disease
AIDS is a collection of diseases caused by infections that may hit a person whose
immune system has been weakened by HIV. AIDS can also include some direct
effects of HIV infection, such as a severe loss of weight and muscle tissue and
damage to the brain and mental functions. Doctors detect HIV and follow the course
of the disease by measuring the amount of the virus in the blood and tissues. They
also count the number of a type of white blood cells called CD4 cells (the helper T
cells) that are infected and destroyed by HIV.
It took a long time and a lot of research to arrive at this definition of AIDS. The 1987
definition of AIDS in adults and adolescents included laboratory evidence of HIV
infection, various opportunistic infections and rare cancers, neurological disease
due to infection of the brain by HIV or by the parasite Taxoplasma, and the HIV
wasting syndrome (a persistent drop in weight and loss of muscle tissue).
The definition was revised and went into effect at the beginning of 1993. It added
conditions such as invasive cervical cancer, recurrent pneumonia, and pulmonary
tuberculosis, as well as a CD4 cell count below 200 cells per cubic millimeter of
blood. (The normal range for CD4 cells is from 500 to 1500 cells per cubic
millimeter.)
AIDS Symptoms
The new case definition adopted by the CDC in 1993 also established a series of
categories from the early to the late stages of HIV/AIDS disease. First, there may be
a short, flu like illness following the first exposure to HIV. Then, there is a long period
in which the person is infected but does not show any symptoms. This period can
last for years, and the person may be unaware that he or she is infected. In the next
stage, the lymph nodes become swollen, because the body is battling the multiplying
virus. Finally, a variety of symptoms and complication appear. Loss of appetite,
weight loss, fever, rashes, night sweats, and fatigue are typical symptoms of AIDS.
The person may also develop memory loss, confusion, and various other mental
problems due to infection of the brain by the virus. Weakening of the immune
system opens the way for opportunistic infections such as Pneumocystis carinii
pneumonia (PCP), Mycobacterium avium complex (MAC), toxoplasmosis,
cytomegalovirus (CMV) and herpes infections, and CMV retinitis (which can cause
blindness). The breakdown of the body's defenses against disease may also allow
various cancers to develop, including Kaposi's sarcoma (KS), lymphomas, and
invasive cervical cancer. Another common effect is the HIV wasting syndrome, a
sever loss of weight and muscle tissue.
Ironically, most of the symptoms typically linked with AIDS are caused not by the
infection itself but by the other diseases that set in after HIV has dangerously
weakened the body's defenses. Coughing and shortness of breath are symptoms of
pneumonia. Rashes and sores on the skin or in the mouth may be caused by
fungus or herpes virus infections. Confusion, memory loss, and other mental
problems may be due to HIV infection, but they can also be caused by attack on the
brain by the parasite Taxoplasma. The purplish Kaposi's sarcoma. The great variety
of opportunistic microbes that can attack a person with AIDS is responsible for the
great variety of symptoms, which made it difficult at first for medical researchers to
determine that they were dealing with a single disease. (If AIDS had been named
later, it probably would not have been called a syndrome, but rather HIV disease.)
Who Gets AIDS?
When AIDS first appeared in the United States, it seemed to be a disease of gay
men. Since then, however, it has become evident that it can strike people of both
sexes, all ages, all races, and all sexual orientations. In United States, the largest
group of people with AIDS is still men who have sex with men (48 percent of all
cases reported up to the end of 1997), but injection drug users account for 25
percent (plus an additional 6 percent who fall into both exposure groups). The
proportions of both men and women who acquired AIDS through heterosexual
contact, after increasing steadily for years, dropped somewhat in 1997, to 9 percent
of the total up to that point. Children under thirteen years of age accounted for only
8086 (a little more than one percent) of the total of 641,086 cases reported in the U.
S. through the end of 1997. The majority of AIDS cases (482,168 or 75 percent)
had been diagnosed in people from age twenty-five to forty-four. Blacks and
Hispanics were represented far in excess of their proportions in the general
population (230,029 and 115,354 cases, or 36 percent and 18 percent of the cases,
respectively). While AIDS was no longer the leading killer of all adults in the twenty-
five to forty-four age groups after the decrease in AIDS deaths in 1996, it was still
the leading killer in that age group for black men and women.
HIV: The AIDS Virus
The life cycle of HIV has two main parts. The first part starts when an HIV virion
attaches itself to the outside of a cell. Its outer membrane merges with the cell's
outer membrane, and the material from the virus's core moves into the cell. There it
is like an uninvited guest that not only makes itself at home but soon starts running
the household. Using the materials of the host cell, the viral enzymes go to work,
copying the HIV genetic material. The completed DNA copy of the HIV genes will be
copied every time the cell divides and reproduces its own genes. In some cells the
life cycle may stop there. The HIV genes may remain quietly hidden among the host
cell's genes, apparently doing nothing at all. This situation may go on for years. But
then something may happen to start off the second part of the virus's life cycle-for
example, when an infected white blood cell is activated to fight invading germs. At
that point the hidden virus uses its host cell as a factory to produce and release new
HIV virions.
The Body Defends Itself
The body's first line of defense against invading germs is a set of barriers: the skin
that covers the outer surface and the slippery, mucus-covered membranes that line
the mouth, nose, and other passages that lead into the body. A cut or sore in these
coverings might allow germs to slip into the bloodstream. Some germs are also
capable of infecting mucous membranes. Cold viruses, for example, can infect cells
in the respiratory tract; HIV can infect cells in the lining of the rectum, vagina, and
penis.
Cells that are attacked by a virus release various chemicals. Some of them act as
distress signals that call in white blood cells, the body's roving defenders. Several
kinds of white blood cells help fight invading germs. Some, called macrophages
(literally, "big cells that eat"), gobble up invading germs, destroying them before
they can infect cells. Others, the lymphocytes, are able to recognize foreign
chemicals, such as the proteins on the outer coat of a virus. Some of these
lymphocyte, called B cells, produce antibodies, proteins that fir parts of virus
proteins. Antibodies attach to viruses, preventing them from attacking their target
cells of making them easier for macrophages to destroy. Antibodies also tag virus-
infected cells, marking them for destruction. Several kinds of lymphocytes are called
T cells. Killer T cells kill infected cells and cancer cells. Helper T cells stimulate B
cells to multiply and produce antibodies. The macrophages, T cells, and B cells are
constantly communicating with one another and coordinating their activities by way
of a stream of chemical messengers carried by the bloodstream and tissue fluids.
Once a person has antibodies that protect against a particular virus, some of the
antibody-producing cells are kept "on file" in the body, ready to leap into action if
the same type of virus attacks again. It generally takes about two weeks to make an
adequate supply of antibodies to fight a virus the body has never met before; during
that time the viruses multiply while the body's less specific defenses try to keep them
in check.
AIDS an all-about guide for young adults
By: Alvin &Virginia Silverstein& Laura Silverstein Nunn
AIDS >
