HIV (Human Immunodeficiency Virus) is a virus that weakens the immune system. It attacks and takes over immune cells, using them to reproduce itself. Infected cells can be found in many parts of the body and in body fluids such as blood, semen, vaginal fluid, breast milk and anal mucous.
AIDS (Acquired Immune Deficiency Syndrome) is a serious weakening of the body’s immune system caused by HIV. When an HIV positive person’s immune cells (CD4 cells) drop below 200, they can be vulnerable to infections that their body would normally fight off.
HIV, not AIDS, is transmitted between people. For more information, see:
- Sexual transmission of HIV
- Non-sexual transmission of HIV: drug use
- Non-sexual transmission of HIV: parent to child
If you think you have been exposed to HIV in the last 72 hours, see Post Exposure Prophylaxis.
Victoria has the second-largest HIV epidemic in Australia, behind New South Wales. It has contained infection rates amongst injecting drug users, sex workers and those who receive blood transfusions. Sexual transmission is still the main cause of HIV infection. Unprotected anal sex between men accounts for about 80% of cases, but transmission through heterosexual sex is slowly increasing.
Annual rates of new HIV infections in Victoria dropped from a peak in 1985 (over 500 cases) to a low in 1999 (141 cases). Since then the rate has climbed again and evened out at roughly 260 cases each year from 2006 to 2010. AIDS diagnoses peaked from 1992 to 1995 (180 cases). New treatments available since the mid-1990s have lead to a drop to around 50 annual cases.
HIV is a notifiable disease which means that the Department of Health is notified of all new HIV diagnoses. Statistics on HIV and AIDS are available from the Victorian HIV Surveillance Data.
Nationally, 80% of HIV diagnoses are men who have sex with men. Cities with bigger communities of men who have sex with men have higher infection rates. Heterosexual infection rates vary. For example, rates have stayed low in South Australia but have climbed to about 50% of all notifications in Western Australia.
The rate of new HIV infections in Australia peaked in 1987 then slowly dropped till 1999. It then climbed and evened out in 2006. The national pattern of AIDS diagnoses is similar to Victoria. Statistics are available from the Kirby Institute.
Around the world
The size and nature of the HIV epidemic varies greatly from country to country. In many western countries, unprotected anal sex between men is the main risk category. However, in sub-Saharan Africa heterosexual sex is the main risk group, and in China most transmission is through intravenous drug use. AIDS diagnoses rates also vary, depending on the availability of HIV treatments.
Not all countries have good reporting systems, so data may not be accurate. Statistics are available from UNAIDS.
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