Definition
of HIV and AIDS
HIV and AIDS are not the same. Everyone
who has AIDS has been infected with HIV; but everyone with
HIV infection does not have AIDS.
The Human Immunodeficiency Virus (HIV)
is a virus that attacks the immune system, the body's natural
ability to protect itself against infections and diseases,
damaging the body's ability to fight diseases and infections.
Without a healthy, functioning immune system, a person is
at risk of infections by bacteria, other viruses and disease-causing
organisms. Some of these infections can cause life-threatening
illnesses.
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This highly magnified transmission electron micrographic
(TEM) image
revealed the presence of mature forms of the human immunodeficiency
virus (HIV) in a tissue sample under investigation.
Courtesy of US Public Health Image Library.
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Acquired ImmunoDeficiency (sometimes Immune
Deficiency) Syndrome (AIDS) is a complex of symptoms and
infections caused by the HIV virus as it impacts the immune
system. It is an acquired infection; it is not hereditary.
A person must come in contact with the virus; it enters the
body through blood and body fluids. As HIV damages the immune
system, infected persons become vulnerable to infections or
diseases known as opportunistic diseases. These opportunistic
infections generally do not pose a threat to persons with
healthy functioning immune systems. The term AIDS applies
to the most advanced stages of an HIV infection. Medical treatments,
particularly the antiretroviral medications, have delayed
the onset of AIDS in persons who are infected with HIV.
How HIV Impacts
the Human Body
When HIV enters the bloodstream, the virus
starts seeking a particular form of white blood cell (lymphocyte)
essential to the functioning of the immune system. This cell
is called a T-Helper lymphocyte. One of its functions
is to "orchestrate" the immune system in the event of attack
from harmful foreign invaders, pathogens such as bacteria,
viruses, and other disease-causing organisms. It is also referred
to as the T4 or the CD4 cell.
When the HIV makes contact with the T-cell,
the T-cell sends signals to other cells which produce antibodies.
Antibodies are produced by the immune system to help get rid
of specific foreign invaders that can cause infection.
Producing antibodies is an essential function
of our immune systems. The body makes a specific antibody
for each infection. For example, if we are exposed to measles
virus, the immune system will develop antibodies specifically
designed to attack the measles virus. Polio antibodies fight
polio virus. When our immune system is working correctly,
it protects against these harmful pathogens.
HIV infects and destroys the T-Helper lymphocytes
and damages their ability to signal for antibody production.
This results in the eventual decline of the immune system.
Progress of HIV
Infection
Viral Transmission
This is the initial infection with HIV. When
a person is infected with HIV, they will probably have virus
circulating in their bloodstream, and may become infectious
to others within five days. The person may be infectious
before the onset of any symptoms. They will remain infectious
for the rest of their lives.
Primary HIV Infection
During the first few weeks of HIV infection,
an infected person has a very high amount of virus in their
bloodstream. The high viral load means the individual may
more easily pass the virus to others. Unfortunately, during
primary infection, many people are unaware that they are infected.
The most common symptoms noticed by persons
newly infected with HIV are fever, swollen glands in the neck,
armpits and/or groin, rash, fatigue and a sore throat (also
common with many other types of infections). This is sometimes
called "seroconversion syndrome" or "seroconversion sickness."
It resembles mononucleosis infection, with similar symptoms
and length of illness.
These initial symptoms go away in a few weeks,
but the individual continues to be infectious to others. It
is extremely important that healthcare providers consider
the diagnosis of HIV primary infection of an individual has
behaviors which put him or her at risk for HIV and is presenting
with the above symptoms. If individuals experience these symptoms
after having unprotected sex or sharing needles, they should
seek medical care and tell their provider why they are concerned
about HIV infection. An HIV antibody test should be done,
but it will only reflect the person's prior HIV status. To
detect acute HIV infection, an HIV RNA test that tests directly
for the HIV virus must be done.
There are many arguments for and against
treatment in primary infection, and healthcare providers have
different opinions regarding whether or not a newly HIV infected
person should start drug therapies immediately.
Seroconversion
Seroconversion is the time period that it
takes from infection to the production of antibodies, which
would show positive on an HIV test. This may vary from person
to person but HIV antibodies are detectable sometime within
the first three to six months of infection, and in most cases
will be detectable for life. This time frame is also known
as the window period, in that the infected person will
test negative for HIV antibodies, if tested prior to seroconversion,
although they are already infected and are able to transmit
the virus to others.
Asymptomatic HIV Infection
During this time period an HIV-infected person
has no noticeable signs or symptoms. The person may look and
feel healthy, but can still pass the virus to others. It is
not unusual for an HIV-infected person to live 10 years or
longer without any outward physical signs of progression to
AIDS. Meanwhile, the person's blood and other systems are
affected by HIV. This would be reflected in laboratory tests.
Unless a person in this stage has been tested for HIV, they
will probably not be aware they are infected.
Symptomatic HIV Infection
HIV Infection During the symptomatic stage
of HIV infection, a person begins to have noticeable physical
symptoms that are related to HIV infection. Although there
are no symptoms that are specific ONLY to HIV infection, some
common symptoms are:
- A persistent low grade fever
- Pronounced weight loss that is not due to dieting
- Persistent headaches
- Diarrhea that lasts more than one month
- Difficulty recovering from colds and the flu
- A person may become sicker than they normally would
- Women may have recurrent vaginal yeast infections
- Thrush (a yeast infection) coating the mouth or tongue
Anyone who has symptoms like these and has engaged in behaviors
that transmit HIV should seek medical advice. The only way
to know for sure if you are infected with HIV is to take an
HIV antibody test.
AIDS
An AIDS diagnosis can only be made by a licensed healthcare
provider. The diagnosis is based on the result of HIV-specific
blood tests, and the person's physical condition. A diagnosis
of AIDS is made because the person has an illness, one of
the "AIDS-defining illnesses", and has white blood cell counts
and other conditions that are specifically linked to making
an AIDS diagnosis. Once a person is diagnosed with AIDS, even
if they later feel better, they do not "go backwards" in the
classification system for HIV infection. This means that they
are always considered to have AIDS.
People who have an AIDS diagnosis may often appear to a casual
observer to be quite healthy, but continue to be infectious
and can pass the virus to others.
Over time, people with AIDS frequently have a reduced white
blood cell count and develop poorer health. They may also
have a significant amount of virus present in their blood,
which is measured as viral load.
HIV Strains and
Subtypes
HIV has divided into two primary strains:
HIV-1 and HIV-2. HIV-1 is found throughout the world; generally
when HIV is referred to without specifying a type of virus,
it is the HIV-1 that is referred to. HIV-2 is found primarily
in West Africa, where the virus may have been in circulation
since the 1960s - 1970s. It is rarely found elsewhere. HIV
is highly variable virus and mutates very easily. This means
that there are many different strains of HIV, even within
the body of a single infected person. Based on genetic similarities,
the numerous virus strains may be classified into types, groups
and sub-types.
The Origin of HIV
Since HIV was discovered in 1983, researchers
have worked to pinpoint the origin of the virus. In 1999,
an international team of researchers reported that they discovered
the origins of HIV-1, the predominant strain of HIV in the
developed world. A subspecies of chimpanzees native to west
equatorial Africa was identified as the original source of
the virus. The researchers believe that HIV-1 was introduced
into the human population in the 1930s and 1940s when hunters
became exposed to infected blood.
Continue to Part 1. Etiology
and Epidemiology of HIV and AIDS, Con't.
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