-- acquired immunodeficiency syndrome -- was first reported
in the United States in 1981 and has since become a major
worldwide epidemic. AIDS is caused by the human immunodeficiency
virus (HIV). By killing or damaging cells of the body's immune
system, HIV progressively destroys the body's ability to fight
infections and certain cancers. People diagnosed with AIDS
may get life-threatening diseases called opportunistic infections,
which are caused by microbes such as viruses or bacteria that
usually do not make healthy people sick.
than 700,000 cases of AIDS have been reported in the United
States since 1981, and as many as 900,000 Americans may be
infected with HIV. The epidemic is growing most rapidly among
minority populations and is a leading killer of African American
males. According to the U.S. Centers for Disease Control and
Prevention (CDC), AIDS affects six times more African Americans
than whites and three times more Hispanics than whites.
HIV is spread most commonly by having sex with an infected
partner. The virus can enter the body through the lining of
the vagina, vulva, penis, rectum, or mouth during sex.
also is spread through contact with infected blood. Before
blood was screened for evidence of HIV infection and before
heat-treating techniques to destroy HIV in blood products
were introduced, HIV was transmitted through transfusions
of contaminated blood or blood components. Today, because
of blood screening and heat treatment, the risk of getting
HIV from such transfusions is extremely small.
frequently is spread among injection drug users by the sharing
of needles or syringes contaminated with very small quantities
of blood from someone infected with the virus. It is rare,
however, for a patient to give HIV to a health care worker
or vice-versa by accidental sticks with contaminated needles
or other medical instruments.
can transmit HIV to their babies during pregnancy or birth.
Approximately one-quarter to one-third of all untreated pregnant
women infected with HIV will pass the infection to their babies.
HIV also can be spread to babies through the breast milk of
mothers infected with the virus. If the mother takes the drug
AZT during pregnancy, she can reduce significantly the chances
that her baby will be infected with HIV. If doctors treat
mothers with AZT and deliver their babies by cesarean section,
the chances of the baby being infected can be reduced to a
rate of 1 percent.
study sponsored by NIAID in Uganda found a highly effective
and safe drug regimen for preventing transmission of HIV from
an infected mother to her newborn that is more affordable
and practical than any other examined to date. Interim results
from the study show that a single oral dose of the antiretroviral
drug nevirapine (NVP) given to an HIV-infected woman in labor
and another to her baby within three days of birth reduces
the transmission rate by half compared with a similar short
course of AZT.
researchers have detected HIV in the saliva of infected individuals,
no evidence exists that the virus is spread by contact with
saliva. Laboratory studies reveal that saliva has natural
properties that limit the power of HIV to infect. Research
studies of people infected with HIV have found no evidence
that the virus is spread to others through saliva such as
by kissing. No one knows, however, whether so-called "deep
kissing," involving the exchange of large amounts of saliva,
or oral intercourse increase the risk of infection. Scientists
also have found no evidence that HIV is spread through sweat,
tears, urine, or feces.
of families of HIV-infected people have shown clearly that
HIV is not spread through casual contact such as the sharing
of food utensils, towels and bedding, swimming pools, telephones,
or toilet seats. HIV is not spread by biting insects such
as mosquitoes or bedbugs.
can infect anyone who practices risky behaviors such as:
drug needles or syringes, or
sexual contact with an infected person without using a condom
or with someone whose HIV status is unknown.
a sexually transmitted disease such as syphilis, genital herpes,
chlamydial infection, gonorrhea, or bacterial vaginosis appears
to make people more susceptible to acquiring HIV infection
during sex with infected partners.
people do not develop any symptoms when they first become
infected with HIV. Some people, however, have a flu-like illness
within a month or two after exposure to the virus. This illness
may include fever, headache, tiredness, and enlarged lymph
nodes (organs of the immune system easily felt in the neck
and groin). These symptoms usually disappear within a week
to a month and are often mistaken for those of another viral
infection. During this period, people are very infectious,
and HIV is present in large quantities in genital fluids.
persistent or severe symptoms may not surface for a decade
or more after HIV first enters the body in adults, or within
two years in children born with HIV infection. This period
of "asymptomatic" infection is highly individual. Some people
may begin to have symptoms as soon as a few months, while
others may be symptom-free for more than 10 years. During
the asymptomatic period, however, the virus is actively multiplying,
infecting, and killing cells of the immune system. HIV's effect
is seen most obviously in a decline in the blood levels of
CD4+ T cells (also called T4 cells) -- the immune system's
key infection fighters. At the beginning of its life in the
human body, the virus disables or destroys these cells without
the immune system deteriorates, a variety of complications
start to take over. For many people, their first sign of infection
is large lymph nodes or "swollen glands" that may be enlarged
for more than three months. Other symptoms often experienced
months to years before the onset of AIDS include:
frequent fevers and sweats,
or frequent yeast infections (oral or vaginal),
skin rashes or flaky skin,
pelvic inflammatory disease in women that does not respond
to treatment, or
people develop frequent and severe herpes infections that
cause mouth, genital, or anal sores, or a painful nerve disease
called shingles. Children may grow slowly or be sick a lot.
term AIDS applies to the most advanced stages of HIV infection.
The CDC in Atlanta, GA, develops official criteria for the
definition of AIDS and is responsible for tracking the spread
of AIDS in the United States.
definition of AIDS includes all HIV-infected people who have
fewer than 200 CD4+ T cells per cubic millimeter of blood.
(Healthy adults usually have CD4+ T-cell counts of 1,000 or
more.) In addition, the definition includes 26 clinical conditions
that affect people with advanced HIV disease. Most of these
conditions are opportunistic infections, which rarely cause
harm in healthy people. In people with AIDS, these infections
are often severe and sometimes fatal because the immune system
is so ravaged by HIV that the body cannot fight off certain
bacteria, viruses, fungi, parasites, and other microbes.
infections common in people with AIDS cause symptoms such
and shortness of breath,
and lack of coordination,
or painful swallowing,
symptoms such as confusion and forgetfulnesss,
and persistent diarrhea,
abdominal cramps, and vomiting,
loss and extreme fatigue,
children with AIDS may get the same opportunistic infections
as adults with the disease, they also experience severe forms
of the bacterial infections which all children may get, such
as conjunctivitis (pink eye), ear infections, and tonsillitis.
with AIDS are particularly prone to developing various cancers,
especially those caused by viruses such as Kaposi's sarcoma
and cervical cancer, or cancers of the immune system known
as lymphomas. These cancers are usually more aggressive and
difficult to treat in people with AIDS. Signs of Kaposi's
sarcoma in light-skinned people are round brown, reddish,
or purple spots that develop in the skin or in the mouth.
In dark-skinned people, the spots are more pigmented.
the course of HIV infection, most people experience a gradual
decline in the number of CD4+ T cells, although some may have
abrupt and dramatic drops in their CD4+ T-cell counts. A person
with CD4+ T cells above 200 may experience some of the early
symptoms of HIV disease. Others may have no symptoms even
though their CD4+ T-cell count is below 200.
people are so debilitated by the symptoms of AIDS that they
cannot hold steady employment or do household chores. Other
people with AIDS may experience phases of intense life-threatening
illness followed by phases in which they function normally.
small number of people (fewer than 50) initially infected
with HIV 10 or more years ago have not developed symptoms
of AIDS. Scientists are trying to determine what factors may
account for their lack of progression to AIDS, such as particular
characteristics of their immune systems or whether they were
infected with a less aggressive strain of the virus, or if
their genes may protect them from the effects of HIV. Scientists
hope that understanding the body's natural method of control
may lead to ideas for protective HIV vaccines and use of vaccines
to prevent the disease from progressing.