1) WHAT DOES "AIDS" MEAN?

AIDS stands for Acquired Immune Deficiency Syndrome:

• Acquired means you can get infected with it;
• Immune Deficiency means a weakness in the body's system that fights diseases.
• Syndrome means a group of health problems that make up a disease.

AIDS is caused by a virus called HIV, the Human Immunodeficiency Virus. If you get infected with HIV, your body will try to fight the infection. It will make "antibodies," special molecules to fight HIV.

http://www.aids.org/factSheets/101-What-is-AIDS.html

2) how powerful HIV can be?

There is no cure for AIDS. There are drugs that can slow down the HIV virus, and slow down the damage to your immune system. There is no way to "clear" the HIV out of your body, consequently it will tend to expand easily through a whole popullation.

3) the effects of HIV on the immune system.

The effects of HIV should be limited to a reduction

in the number of active lymphocytes and a loss of

the ability to produce antibodies.

4) is it possible to prevent HIV?

The extent to which individuals in different societies can minimize or eliminate each of these risks could be considered, but principally taking into consideration that AIDS is transmitted during intercourse condom could be a partial prevention.