AIDS / HIV Terms Listed
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AIDS - 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.
More than 830,000 cases of AIDS have been reported in the
United States since 1981. As many as 950,000 Americans may
be infected with HIV, one-quarter of whom are unaware of
their infection. The epidemic is growing most rapidly among
minority populations and is a leading killer of African-American
males ages 25 to 44. According to the U.S. Centers for Disease
Control and Prevention (CDC), AIDS affects nearly seven
times more African Americans and three times more Hispanics
than whites.
HOW IS HIV TRANSMITTED?
HIV is spread most commonly by having unprotected sex with
an infected partner. The virus can enter the body through
the lining of the vagina, vulva, penis, rectum, or mouth
during sex.
HIV also is spread through contact with infected blood.
Before donated 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.
HIV 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.
Women 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
significantly reduce the chances that her baby will get
infected with HIV. If health care providers 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.
A study sponsored by the National Institute of Allergy
and Infectious Diseases (NIAID) in Uganda found a highly
effective and safe drug for preventing transmission of HIV
from an infected mother to her newborn. This regimen is
more affordable and practical than any other examined to
date. 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 of HIV
by half compared with a similar short course of AZT.
Although researchers have found HIV in the saliva of infected
people, there is no evidence 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
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.
Studies 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.
HIV can infect anyone who practices risky behaviors such
as
Sharing drug needles or syringes
Having sexual contact with an infected person without using
a condom
Having sexual contact with someone whose HIV status is unknown
Having a sexually transmitted disease such as syphilis,
genital herpes, chlamydial infection, gonorrhea, or bacterial
vaginosis appears to make people more susceptible to getting
HIV infection during sex with infected partners.
SYMPTOMS OF HIV INFECTION
Many people do not have 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
Enlarged lymph nodes (glands 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.
More persistent or severe symptoms may not appear for 10
years 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 within
a few months, while others may be symptom-free for more
than 10 years.
Even during the asymptomatic period, the virus is actively
multiplying, infecting, and killing cells of the immune
system. The most obvious effect of HIV infection is a decline
in the number of CD4 positive T cells (also called T4 cells)
found in the blood -- 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 causing
symptoms.
As the immune system worsens, a variety of complications
start to take over. For many people, the first signs of
infection are 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
Lack of energy
Weight loss
Frequent fevers and sweats
Persistent or frequent yeast infections (oral or vaginal)
Persistent skin rashes or flaky skin
Pelvic inflammatory disease in women that does not respond
to treatment
Short-term memory loss
Some 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.
AIDS
The term AIDS applies to the most advanced stages of HIV
infection. CDC developed official criteria for the definition
of AIDS and is responsible for tracking the spread of AIDS
in the United States.
CDC's definition of AIDS includes all HIV-infected people
who have fewer than 200 CD4 positive T cells (abbreviated
CD4+ T cells) per cubic millimeter of blood (Healthy adults
usually have CD4 positive 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 that generally do
not affect 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.
Symptoms of opportunistic infections common in people with
AIDS include
Coughing and shortness of breath
Seizures and lack of coordination
Difficult or painful swallowing
Mental symptoms such as confusion and forgetfulness
Severe and persistent diarrhea
Fever
Vision loss
Nausea, abdominal cramps, and vomiting
Weight loss and extreme fatigue
Severe headaches
Coma
Children with AIDS may get the same opportunistic infections
as do adults with the disease. In addition, they also have
severe forms of the bacterial infections all children may
get, such as conjunctivitis (pink eye), ear infections,
and tonsillitis.
People 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.
During the course of HIV infection, most people experience
a gradual decline in the number of CD4 positive T cells;
although some may have abrupt and dramatic drops in their
CD4 positive T-cell counts. A person with CD4 positive T
cells above 200 may experience some of the early symptoms
of HIV disease. Others may have no symptoms even though
their CD4 positive T-cell count is below 200.
Many 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.
A small number of people first 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.
DIAGNOSIS
Because early HIV infection often causes no symptoms, a
doctor or other health care provider usually can diagnose
it by testing a person's blood for the presence of antibodies
(disease-fighting proteins) to HIV. HIV antibodies generally
do not reach detectable levels in the blood for one to three
months following infection. It may take the antibodies as
long as six months to be produced in quantities large enough
to show up in standard blood tests.
People exposed to the virus should get an HIV test as soon
as they are likely to develop antibodies to the virus -
within 6 weeks to 12 months after possible exposure to the
virus. By getting tested early, people with HIV infection
can discuss with a health care provider when they should
start treatment to help their immune systems combat HIV
and help prevent the emergence of certain opportunistic
infections (see section on treatment below). Early testing
also alerts HIV-infected people to avoid high-risk behaviors
that could spread the virus to others.
Most health care providers can do HIV testing and will
usually offer counseling to the patient at the same time.
Of course, individuals can be tested anonymously at many
sites if they are concerned about confidentiality.
Health care providers diagnose HIV infection by using two
different types of antibody tests, ELISA and Western Blot.
If a person is highly likely to be infected with HIV and
yet both tests are negative, the health care provider may
request additional tests. The person also may be told to
repeat antibody testing at a later date, when antibodies
to HIV are more likely to have developed.
Babies born to mothers infected with HIV may or may not
be infected with the virus, but all carry their mothers'
antibodies to HIV for several months. If these babies lack
symptoms, a doctor cannot make a definitive diagnosis of
HIV infection using standard antibody tests until after
15 months of age. By then, babies are unlikely to still
carry their mothers' antibodies and will have produced their
own, if they are infected. Health care experts are using
new technologies to detect HIV itself to more accurately
determine HIV infection in infants between ages 3 months
and 15 months. They are evaluating a number of blood tests
to determine if they can diagnose HIV infection in babies
younger than 3 months.
TREATMENT
When AIDS first surfaced in the United States, there were
no medicines to combat the underlying immune deficiency
and few treatments existed for the opportunistic diseases
that resulted. During the past 10 years, however, researchers
have developed drugs to fight both HIV infection and its
associated infections and cancers.
The U.S. Food and Drug Administration (FDA) has approved
a number of drugs for treating HIV infection. The first
group of drugs used to treat HIV infection, called nucleoside
reverse transcriptase (RT) inhibitors, interrupts an early
stage of the virus making copies of itself. Included in
this class of drugs (called nucleoside analogs) are AZT,
ddC (zalcitabine), ddI (dideoxyinosine), d4T (stavudine),
3TC (lamivudine), abacavir (ziagen), and tenofovir (viread).
These drugs may slow the spread of HIV in the body and delay
the start of opportunistic infections.
Health care providers can prescribe non-nucleoside reverse
transcriptase inhibitors (NNRTIs), such as delvaridine (Rescriptor),
nevirapine (Viramune), and efravirenz (Sustiva), in combination
with other antiretroviral drugs.
FDA also has approved a second class of drugs for treating
HIV infection. These drugs, called protease inhibitors,
interrupt virus replication at a later step in its life
cycle. They include
Ritonavir (Norvir)
Saquinivir (Invirase)
Indinavir (Crixivan)
Amprenivir (Agenerase)
Nelfinavir (Viracept)
Lopinavir (Kaletra)
Because HIV can become resistant to any of these drugs,
health care providers must use a combination treatment to
effectively suppress the virus. When RT inhibitors and protease
inhibitors are used in combination, it is referred to as
highly active antiretroviral therapy, or HAART, and can
be used by people who are newly infected with HIV as well
as people with AIDS.
Researchers have credited HAART as being a major factor
in significantly reducing the number of deaths from AIDS
in this country. While HAART is not a cure for AIDS, it
has greatly improved the health of many people with AIDS
and it reduces the amount of virus circulating in the blood
to nearly undetectable levels. Researchers, however, have
shown that HIV remains present in hiding places, such as
the lymph nodes, brain, testes, and retina of the eye, even
in patients who have been treated.
Despite the beneficial effects of HAART, there are side
effects associated with the use of antiviral drugs that
can be severe. Some of the nucleoside RT inhibitors may
cause a decrease of red or white blood cells, especially
when taken in the later stages of the disease. Some may
also cause inflammation of the pancreas and painful nerve
damage. There have been reports of complications and other
severe reactions, including death, to some of the antiretroviral
nucleoside analogs when used alone or in combination. Therefore,
health care experts recommend that people on antiretroviral
therapy be routinely seen and followed by their health care
providers. The most common side effects associated with
protease inhibitors include nausea, diarrhea, and other
gastrointestinal symptoms. In addition, protease inhibitors
can interact with other drugs resulting in serious side
effects.
A number of drugs are available to help treat opportunistic
infections to which people with HIV are especially prone.
These drugs include
Foscarnet and ganciclovir to treat cytomegalovirus (CMV)eye
infections
Fluconazole to treat yeast and other fungal infections
Trimethoprim/sulfamethoxazole (TMP/SMX) or pentamidine to
treat Pneumocystis carinii pneumonia (PCP)
In addition to antiretroviral therapy, health care providers
treat adults with HIV, whose CD4+ T-cell counts drop below
200, to prevent the occurrence of PCP, which is one of the
most common and deadly opportunistic infections associated
with HIV. They give children PCP preventive therapy when
their CD4+ T-cell counts drop to levels considered below
normal for their age group. Regardless of their CD4+ T-cell
counts, HIV-infected children and adults who have survived
an episode of PCP take drugs for the rest of their lives
to prevent a recurrence of the pneumonia.
HIV-infected individuals who develop Kaposi's sarcoma or
other cancers are treated with radiation, chemotherapy,
or injections of alpha interferon, a genetically engineered
protein that occurs naturally in the human body.
PREVENTION
Because no vaccine for HIV is available, the only way to
prevent infection by the virus is to avoid behaviors that
put a person at risk of infection, such as sharing needles
and having unprotected sex.
Many people infected with HIV have no symptoms. Therefore,
there is no way of knowing with certainty whether a sexual
partner is infected unless he or she has repeatedly tested
negative for the virus and has not engaged in any risky
behavior.
People should either abstain from having sex or use male
latex condoms or female polyurethane condoms, which may
offer partial protection, during oral, anal, or vaginal
sex. Only water-based lubricants should be used with male
latex condoms.
Although some laboratory evidence shows that spermicides
can kill HIV, researchers have not found that these products
can prevent a person from getting HIV.
The risk of HIV transmission from a pregnant woman to her
baby is significantly reduced if she takes AZT during pregnancy,
labor, and delivery, and if her baby takes it for the first
six weeks of life.
RESEARCH
NIAID-supported investigators are conducting an abundance
of research on all areas of HIV infection, including developing
and testing preventive HIV vaccines and new treatments for
HIV infection and AIDS- associated opportunistic infections.
Researchers also are investigating exactly how HIV damages
the immune system. This research is identifying new and
more effective targets for drugs and vaccines. NIAID-supported
investigators also continue to trace how the disease progresses
in different people.
Scientists are investigating and testing chemical barriers,
such as topical microbicides, that people can use in the
vagina or in the rectum during sex to prevent HIV transmission.
They also are looking at other ways to prevent transmission,
such as controlling sexually transmitted diseases and modifying
people's behavior, as well as ways to prevent transmission
from mother to child.
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