AIDS (or the acquired immunodeficiency syndrome) is a viral disease caused by HIV.
The AIDS agent is a Lentivirus, HIV (HIV-1 and HIV-2) for human immunodeficiency virus. It infects immune system cells, T4 lymphocytes which carry the appropriate receptor (CD4 protein), but can also infect other cell types.
Transmission of AIDS
The virus is transmitted through specific body fluids in which viral particles are found. It may be transmitted sexually (by genital secretions), through blood (by transfusion or needle-sharing) or from mother to fetus (by blood-placental spread, during childbirth or whenbreast-feeding).
According to the WHO and Onusida estimates, there were 33.4 million people living with HIV at the end of 2008.
Symptoms of AIDS
There are three phases of infection with the AIDS virus.
- Primary infection, in which the number of virions in the body increases greatly immediately after infection and then falls rapidly as a result of the action of the immune system.
- There is then an asymptomatic phase, in which the patient has no symptoms of the disease. T lymphocytes are, however, progressively destroyed by HIV. At this stage, the person has antibodies against the virus and is said to be seropositive.
- When the immune system is too weak (CD4 lymphocytes and macrophages have been destroyed), which may take 10 to 15 years or even more, the symptoms of the disease develop: this is AIDS. Opportunistic diseases, particularly tuberculosis, but also pneumonias,herpes infections, or cancers (Kaposi sarcoma, lymphomas etc.) develop.
Treatment of AIDS
It is not yet possible to cure AIDS, as the viral genome incorporates itself into the cell and therefore remains latent and invisible to the immune system. It is therefore important to protect against infection, for example by using a condom.
Nevertheless, there are treatments to slow the progression of the disease towards the AIDS stage. These involve antivirals, which are not sufficiently effective on their own but are more effective when they are taken in combination. When three are given, the term triple-therapy is used.
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Use of a condom protects against HIV infection. © DR