HIV stands for Human Immunodeficiency Virus. It was first isolated in Paris in 1983 by Dr Luc Montagnier. HIV belongs to a group of viruses called retroviruses, known for their capacity to copy their genetic blueprint onto the genes of the infected person's own cells.

Unlike influenza viruses, which infect cells in the respiratory tract and spread through coughs and sneezes, HIV selectively infects and destroys an integral part of the human immune system - the white blood cells, in particular the T4+ lymphocytes (or CD4 cells).

Acquired Immuno Deficiency Syndrome (AIDS) is characterised by the progressive loss of the CD4+ helper/inducer subset of T lymphocytes, leading to severe immunosuppression and constitutional disease, neurological complications, and opportunistic infections and neoplasms that rarely occur in persons with intact immune function.

Although the precise mechanisms leading to the destruction of the immune system have not been fully delineated, abundant epidemiologic, virologic and immunologic data support the conclusion that infection with the human immunodeficiency virus (HIV) is the underlying cause of AIDS.

AIDS represents only the end stage of a continuous, progressive pathogenic process, beginning with primary infection with HIV, continuing with a chronic phase that is usually asymptomatic, leading to progressively severe symptoms and, ultimately, profound immunodeficiency and opportunistic infections and neoplasms.

Who can be infected with HIV? Anyone. A virus doesn't recognise risk groups. HIV has affected gay men, lesbians, heterosexuals and bisexuals. It is found in all races, nationalities and age groups.

AIDS Diagnosis is based on several factors, including the presence of HIV antibodies and:
Blood tests showing that the counts of white blood cells, called T lymphocytes, have fallen below 200 per millilitre or:
The presence of one or more conditions or opportunistic infections included in the U.S. Centers for Disease Control and Prevention's (CDC) definition of AIDS.

Clinicians and researchers can usually measure the progress of HIV disease in a given individual long before the occurrence of any opportunistic infections. As HIV gains hold throughout the body, CD4 cells begin to decline.

When their number per millilitre of blood is less than 300, the person in question is usually at risk for one or more opportunistic infections. When it drops below 200, s/he has CDC-defined AIDS.

Worldwide, 1,025,073 cases of AIDS were reported to the World Health Organisation (WHO) through December 1994, an increase of 20 percent since December 1993 (WHO, 1995).

Allowing for under-diagnosis, incomplete reporting and reporting delay, and based on the available data on HIV infections around the world, the WHO estimates that over 4.5 million AIDS cumulative cases had occurred worldwide by late 1994 and that 19.5 million people worldwide had been infected with HIV since the beginning of the epidemic (WHO, 1995).

By the year 2000, the WHO estimates that 30 to 40 million people will have been infected with HIV and that 10 million people will have developed AIDS (WHO, 1994).

Causative and risk factors are the same for HIV and AIDS. HIV and AIDS are spread by sexual contact with an infected person, by needle-sharing among injecting drug users (IDUs), or, less commonly (and now very rarely in countries where blood is screened for HIV antibodies), through transfusions of infected blood or blood clotting factors.

Babies born to HIV-infected women may become infected before or during birth, or through breast-feeding after birth. In the health-care setting, workers have been infected with HIV after being stuck with needles containing HIV-infected blood or, less frequently, after infected blood gets into the worker's bloodstream through an open cut or splashes into a mucous membrane.

HIV disease is not uniformly expressed in all individuals. A small proportion of persons infected with the virus develop AIDS and die within months following primary infection, while approximately 5 percent of HIV-infected individuals exhibit no signs of disease progression even after 12 or more years.

Host factors such as age or genetic differences among individuals, the level of virulence of the individual strain of virus, as well as influences such as co-infection with other microbes may determine the rate and severity of HIV disease expression in different people.

Such variables have been termed "clinical illness promotion factors" or co-factors and appear to influence the onset of clinical disease among those infected with any pathogen.

During 1994, 972 cases of HIV infection were newly diagnosed in Australia and exposure to HIV was initially attributed to sources other than male homosexual or bisexual contact and mother-to-child transmission for 304 people (31%).

Of these 304 cases included in the assessment, most (72%) were male and approximately 50% were diagnosed in New South Wales . Overall, 44% of these 304 cases attributed their exposure to HIV to heterosexual contact but for 41%, exposure to HIV was not reported. Males represented 85% of cases for which exposure to HIV was not reported.

For people already infected with the virus, new treatments and drugs offer hope and research is the key to better outcomes and prolonged life. 'Combination Therapies' have proven in early research to be the most effective weapon against these viruses.

HIV is a kind of virus called a retrovirus. It uses the cells in your body to make more virus. Drugs that fight HIV are known as antiretrovirals. The most well known antiretroviral drugs are nucleoside analogues. These include the drugs AZT, ddI, ddC, d4T and 3TC.

Another newer class of drugs used to treat AIDS and HIV disease arecalled protease inhibitors. Antiretroviral drugs are now being used in combinations that have been shown to dramatically reduce the amount of HIV in the body. These combinations have also been shown to help people stay healthy and live longer.

In order to reduce the incidence of new HIV/AIDS diagnoses, the best weapon is that of education. As HIV/AIDS has no known cure, governments and health organisations are focussing on prevention. Safe sex messages, the targeting of groups who have high-risk behaviours and providing clean needles to injecting drug users all contribute to reducing the incidence of new exposures.

There are many HIV and AIDS resources available online. These include government sites, HIV/AIDS organisations, as well as personal accounts and homepages of people living with HIV/AIDS.