What is HIV?
HIV stands for human immunodeficiency virus. It is the virus that causes AIDS. A member of a group of viruses called retroviruses, HIV infects human cells and uses the energy and nutrients provided by those cells to grow and reproduce.
What is AIDS?
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 a weakened 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, as defined by the U.S. Centers for Disease Control and Prevention (CDC), 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.
How is HIV transmitted?
A person who has HIV carries the virus in certain body fluids, including blood, semen, vaginal secretions, and breast milk. The virus can be transmitted only if such HIV-infected fluids enter the bloodstream of another person. This kind of direct entry can occur (1) through the linings of the vagina, rectum, mouth, and the opening at the tip of the penis; (2) through intravenous injection with a syringe; or (3) through a break in the skin, such as a cut or sore. Usually, HIV is transmitted through:
* Unprotected sexual intercourse (either vaginal or anal) with someone who has HIV. Women are at greater risk of HIV infection through vaginal sex than men, although the virus can also be transmitted from women to men. Anal sex (whether male-male or male-female) poses a high risk mainly to the receptive partner, because the lining of the anus and rectum is extremely thin and is filled with small blood vessels that can be easily injured during intercourse.
* Unprotected oral sex with someone who has HIV . There are far fewer cases of HIV transmission attributed to oral sex than to either vaginal or anal intercourse, but oral-genital contact poses a clear risk of HIV infection, particularly when ejaculation occurs in the mouth. This risk goes up when either partner has cuts or sores, such as those caused by sexually transmitted infections (STIs), recent tooth-brushing, or canker sores, which can allow the virus to enter the bloodstream.
* Sharing needles or syringes with someone who is HIV infected. Laboratory studies show that infectious HIV can survive in used syringes for a month or more. That's why people who inject drugs should never reuse or share syringes, water, or drug preparation equipment. This includes needles or \tsyringes used to inject illegal drugs such as heroin, as well as steroids. Other types of needles, such as those used for body piercing and tattoos, can also carry HIV.
* Infection during pregnancy, childbirth, or breast-feeding (mother-to-infant transmission). Any woman who is pregnant or considering becoming pregnant and thinks she may have been exposed to HIV-even if the exposure occurred years ago-should seek testing and counseling. In the U.S., mother-to-infant transmission has dropped to just a few cases each year because pregnant women are routinely tested for HIV. Those who test positive can get drugs to prevent HIV from being passed on to a fetus or infant, and they are counseled not to breast-feed.
Are there treatments for HIV/AIDS?
For many years, there were no effective treatments for AIDS. Today, a number of drugs are available to treat HIV infection and AIDS. Some of these are designed to treat the opportunistic infections and illnesses that affect people with HIV/AIDS. In addition, several types of drugs seek to prevent HIV itself from reproducing and destroying the body's immune system:
* Reverse transcriptase inhibitors attack an HIV enzyme called reverse transcriptase. They include abacavir, delavirdine, didanosine (ddl), efavirenz, emtricitabine (FTC), lamivudine (3TC), nevirapine, stavudine (d4T), tenofovir, zalcitabine (ddC), and zidovudine (AZT);
* Protease inhibitors attack the HIV enzyme protease and include amprenavir, atazanavir, fosamprenavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, tipranavir, and darunavir.
* Fusion inhibitors stop virus from entering cells. To date, only one fusion inhibitor, enfuvirtide, has been approved by the Food and Drug Administration.
Many HIV patients take these drugs in combination-a regimen known as highly active antiretroviral therapy (HAART). When taken as directed, anti-HIV treatment can reduce the amount of HIV in the bloodstream to very low levels and sometimes enables the body's immune cells to rebound to normal levels. Several drugs can be taken to help prevent a number of opportunistic infections including Pneumocystis carinii pneumonia, toxoplasmosis, cryptococcus and cytomegalovirus infection. Once opportunistic infections occur, the same drugs can be used at higher doses to treat these infections, and chemotherapy drugs are available to treat the cancers that commonly occur in AIDS.
Researchers are continuing to develop new drugs that act at critical steps in the virus's life cycle. Efforts are under way to identify new targets for anti-HIV medications and to discover ways of restoring the ability of damaged immune systems to defend against HIV and the many illnesses that affect people with HIV. Ultimately, advances in rebuilding the immune systems of HIV patients will benefit people with a number of serious illnesses, including cancer, Alzheimer's disease, multiple sclerosis, and immune deficiencies associated with aging and premature birth.
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.
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