What is HIV?

HIV stands for 'human immunodeficiency virus'. HIV is a virus (of the type called retrovirus) that infects cells of the human immune system (mainly CD4 positive T cells and macrophages key components of the cellular immune system), and destroys or impairs their function.

Infection with this virus results in the progressive deterioration of the immune system, leading to 'immune deficiency'.

The immune system is considered deficient when it can no longer fulfill its role of fighting off infections and diseases. Immunodeficient people are more susceptible to a wide range of infections, most of which are rare among people without immune deficiency. Infections associated with severe immunodeficiency are known as 'opportunistic infections', because they take advantage of a weakened immune system.

What is AIDS?

AIDS stands for 'acquired immunodeficiency syndrome' and is a surveillance definition based on signs, symptoms, infections, and cancers associated with the deficiency of the immune system that stems from infection with HIV.

What are the symptoms of HIV?

Most people infected with HIV do not know that they have become infected, because they do not feel ill immediately after infection. However, some people at the time of seroconversion develop "Acute retroviral syndrome" which is a glandular fever-like illness with fever, rash, joint pains and enlarged lymph nodes.

Seroconversion refers to the development of antibodies to HIV and usually takes place between 1 and 6 weeks after HIV infection has happened.

Whether or not HIV infection causes initial symptoms, an HIV-infected person is highly infectious during this initial period and can transmit the virus to another person. The only way to determine whether HIV is present in a person's body is by testing for HIV antibodies or for HIV itself.

After HIV has caused progressive deterioration of the immune system, increased susceptibility to infections may lead to symptoms.

An estimated 33 million people were living with HIV in 2007. There were 2.7 million new HIV infections and 2 million AIDS-related deaths last year. The rate of new HIV infections has fallen in several countries, but globally these favourable rends are at least partially offset by increases in new infections in other countries.

Globally, women account for half of all HIV infectionsâ€"this percentage has remained stable for the past several years.

The global percentage of adults living with HIV has levelled off since 2000. In virtually all regions outside sub-Saharan Africa, HIV disproportionately affects people who inject drugs, men who have sex with men and sex workers.

An estimated 33 million people were living with HIV in 2007. There were 2.7 million new HIV infections and 2 million AIDS-related deaths last year.

The rate of new HIV infections has fallen in several countries, but globally these favourable trends are at least partially offset by increases in new infections in other countries.

Globally, women account for half of all HIV infectionsâ€"this percentage has remained stable for the past several years.

The global percentage of adults living with HIV has levelled off since 2000. In virtually all regions outside sub-Saharan Africa, HIV disproportionately affects people who inject drugs, men who have sex with men and sex workers.