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HIV

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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