AIDS stands for Acquired ImmunoDeficiency Syndrome.

It is a disease in which the body's immune system breaks down and is unable to fight off infections, known as "opportunistic infections," and other illnesses that take advantage of aweakened immune system. When a person is infected with HIV, the virus enters the body and lives and multiplies primarily in the white blood cells. These are immune cells that normally protect us from disease.

The hallmark of HIV infection is the progressive loss of a specific type of immune cell called T-helper, or CD4, cells. As the virus grows, it damages or kills these and other cells, weakening the immune system and leaving the person vulnerable to various opportunistic infections and other illnesses ranging from pneumonia to cancer.

A person can receive a clinical diagnosis of AIDS, if he or she has tested positive for HIV and meets one or both of these conditions:

• The presence of one or more AIDS-related infections or illnesses
• A CD4 count that has reached or fallen below 200 cells per cubic millimeter of blood. Also called the T-cell count, the CD4 count ranges from 450 to 1200 in healthy individuals

How quickly do people infected with HIV develop AIDS?

In some people, the T-cell decline and opportunistic infections that signal AIDS develop soon after infection with HIV. But most people do not develop symptoms for 10 to 12 years, and a few remain symptom-free for much longer. As with most diseases, early medical care can help prolong a person's life.

Is there a cure for AIDS?

There is still no cure for AIDS. And while new drugs are helping some people who have HIV live longer, healthier lives, there are many problems associated with them:
• Anti-HIV drugs are highly toxic and can cause serious side effects, including heart damage, kidney failure, and osteoporosis. Many (perhaps even most) patients cannot tolerate long-term treatment with HAART.
• HIV mutates quickly. Even among those who do well on HAART, roughly
half of patients experience treatment failure within a year or two, often because the virus develops resistance to existing drugs. In fact, as many as 10 to 20 percent of newly infected Americans are acquiring viral strains that may already be resistant to current drugs.
• Because treatment regimens are unpleasant and complex, many patients miss doses of their medication. Failure to take anti-HIV drugs on schedule and in the prescribed dosage encourages the development of new drug resistant viral strains.
• Even when patients respond well to treatment, HAART does not eradicate HIV. The virus continues to replicate at low levels and often remains hidden in "reservoirs" in the body, such as in the lymph nodes and brain.