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Introduction To HIV And AIDS
HIV(human immunodeficiency virus)
It was originally isolated in Paris in May 1983 by Luc Montagnier. It belongs
to a group of viruses called retroviruses. Viruses copy their genetic material
into the genetic material of human cells. This means that infected cells stay
infected for the rest of their lives. Through mechanisms which are still not
fully understood, HIV prevents the immune system from working properly.
Normally, the body's immune system would fight off infection. But HIV is able
to infect key cells (called CD4 T-cells) which coordinate the immune system's
fight against infection. Many are actually destroyed by being infected; others,
including CD4 T-cells which are not themselves infected, no longer work
properly. The life-cycle of HIV is discussed in detail in Anti-HIV therapy:
Ways of attacking HIV.
AIDS (acquired immune deficiency syndrome)
AIDS is the result of damage to the immune system. A damaged immune system is
unable to protect the body against certain specific 'opportunistic' infections
and tumours. These are called opportunistic because they are caused by
organisms which are normally controlled by the immune system but which 'take
the opportunity' to cause disease if the immune system has been damaged. Unlike
most other diseases, different people with AIDS may experience different
clinical problems, depending on which specific opportunistic infections they
develop. This is what a syndrome means – a collection of different signs and
symptoms that are all part of the same underlying medical condition. The
opportunistic infections which are considered to be `AIDS-defining' are listed
in the US Centers for Disease Control and Prevention (CDC) classification (see
CDC case definition, 1993 in Introduction to HIV and AIDS: Definitions).
Caues Of AIDS It is widely accepted throughout the scientific community that infection with
HIV is the necessary precondition for the development of AIDS. It is of course
possible for someone's immune system to be compromised in other ways, and in
rare cases this can lead to same kinds of infections seen in AIDS. When an
HIV-negative person experiences immune suppression, there is usually another
quite obvious cause, such as the drugs given after an organ transplantation.
However, the tiny number of cases where no cause can be identified are termed
idiopathic CD4+ lymphocytopenia or ICL.
Although it is clear that HIV has a
central role in the development of AIDS, there remain unanswered
questions about some of the specific mechanisms by which it damages the immune
system. The human immune system is immensely complex and there are many ways in
which it can be affected by a retrovirus such as HIV. Furthermore, it is not
clear what role (if any) other factors – known as co-factors – may play in the
development of immune damage.
Transmission Of HIV: HIV is present in the blood (including menstrual blood), semen and vaginal
fluids of infected people, but can only be passed on to another person if those
fluids get into that person's body. Although sophisticated laboratory
techniques are able to isolate the virus from other body fluids of infected
people (such as saliva), the level of virus in these fluids is far too low to
be infectious.
The main ways in which HIV is transmitted are:
Through unprotected anal or vaginal sex. HIV is unable to pass through good
quality condoms, such as those bearing the British Standard kitemark.
Through blood to blood contact. This mainly happens through the sharing of
injecting equipment among injecting drug users. In the past, before screening
was introduced, this also occurred through blood transfusions or from infected
blood products such as the Factor VIII used to treat haemophilia. Very rarely,
it can happen through occupational accidents amongst healthcare workers, such
as needle-stick injuries. Fortunately, follow-up studies have shown that fewer
than 1% of individuals who receive injuries with HIV-contaminated needles
become infected.
Vertically, from an HIV-positive woman to her baby during the course of
pregnancy, birth or breast-feeding. The average risk of transmission during
pregnancy is in the region of 10-15%, although it may be greater if the mother
has a high viral load (the amount of HIV in her blood, which indicates the rate
at which the virus is reproducing in the body) or has developed AIDS.
Breast-feeding does carry a risk of transmission, and should be avoided in
countries where good alternatives to the mother's milk are available.
The Detection Of HIV:Usually, HIV infection is detected by an HIV antibody test. The first test to be
done, usually on blood, but possibly on saliva, is an ELISA (Enzyme Linked
Immunosorbent Assay). Since this test can sometimes be positive
even when someone is not infected — a `false positive' — a second test called
the Western Blot is done. This can confirm an ELISA.
The amount of time between getting HIV infection and developing antibodies
varies very widely. The vast majority of people with HIV will produce
antibodies by around 45 days after infection. However, in a small proportion it
may take up to six months for antibodies to develop, and in a very few people
with HIV infection it may take even longer. This is one reason why a lack of
HIV antibodies does not always mean freedom from infection.
It is important to bear in mind that the HIV antibody test is not an `AIDS
test': there is no such thing. It is simply a test for one of the results of
HIV infection. For instance, the fact that you can find antibodies to HIV in
saliva does NOT mean that you can find virus there in any quantity.
There are also a number of tests which can look for the virus or parts of the
virus itself (antigen testing and RNA viral load testing), damage to the immune
system, or other aspects of the body's response to the effects of the virus.
These should not be confused with the HIV antibody test.
Symptoms and illnesses:
Anaemia, Anorexia, Anxiety, Blackouts & fits, Breathlessness, Bruising,
Cough, Dermatitis, Diarrhoea, Dry mouth Dry skin, Fatigue, Fevers, Gingivitis
(gum problems), Headaches, Hearing loss, Insomnia, Memory problems, Mouth
infections
Allergy, Aspergillosis, B19 parvovirus, Bacterial infections, Blastomycosis,
Cancers - overview, Candidiasis, Cardiomyopathy, Coccidioidomycosis,
Cryptococcus, Cryptosporidiosis, Cytomegalovirus (CMV) - overview,
Cytomegalovirus (CMV) - key research on treatment, Cytomegalovirus (CMV) - key
research on prophylaxis, Cytomegalovirus (CMV) - references, Depression,
Diabetes, Entamoeba histolytica, Giardia lamblia, Gingivitis
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