Acquired immunodeficiency syndrome (AIDS) is a fatal disease that was first reported in the United States in 1981 and has since become a major worldwide epidemic. By the end of 1999, more than 600,000 Americans had been diagnosed with AIDS, which began its spread among male homosexuals but is now more prevalent among minority populations.

Nearly a million Americans may be infected with the human immunodeficiency virus (HIV), which is the cause of AIDS. The progression from HIV infection to AIDS usually occurs within 10 years. With the development of new and more potent antiviral drugs, scientists hope that the time between HIV infection and the development of AIDS will lengthen.

HIV Infection

HIV kills or impairs cells of the immune system, progressively destroying the body's ability to fight infections and certain cancers. It does this by multiplying within and ultimately destroying cells called T4 lymphocytes (T cells or CD4 cells), which are central to proper functioning of the body's immune defenses.

Blood, semen, saliva, tears, nervous system tissue, breast milk, and vaginal secretions can all harbor the virus. Most often, the virus enters the body through the lining of the vagina, vulva, penis, rectum, or mouth during homosexual or heterosexual sex. HIV is readily spread among drug users who share needles and syringes contaminated with infected blood. Rarely, HIV is transmitted to or from a healthcare worker through accidental sticks with contaminated needles. Before universal screening of blood donors and the introduction of reliable techniques to destroy HIV in blood products, HIV could be transmitted through blood transfusions. In the past, many people with hemophilia acquired AIDS through blood transfusions with infected blood products.

One quarter to one third of all untreated pregnant women who are infected with HIV transmit the virus to their fetuses during pregnancy or childbirth. Drug treatment during pregnancy and cesarean section can reduce this transmission rate to 1 percent.

People infected with HIV may experience a flulike illness within a month or two of exposure to the virus; many have no symptoms. This symptom-free period lasts from a few months to a decade, although the virus is actively multiplying, infecting, and killing immune system cells during this time. The only sign of this virulent activity may be a decline in blood levels of CD4 cells from a normal level of about 1,000. Once a person's CD4-cell count falls below 200, he or she is considered to have AIDS. By that time, other signs of the immune system's deterioration have appeared: swollen glands, lack of energy, weight loss, frequent fevers and sweats, persistent or frequent yeast infections, skin rashes, short-term memory loss, frequent and severe herpes infections, or a painful nerve disease called shingles.

Confirmation of HIV infection involves testing a blood sample for the presence of antibodies to fight the virus, which may not reach detectable levels for 1 to 3 months after exposure. A negative test result (meaning that no antibodies to the virus were detected in the blood) should be followed by repeated testing after 6 months if the person is still at risk or has symptoms.

Early diagnosis has become increasingly important as researchers have identified more effective drugs that, when used in combination, seem to delay development of the disease. These include drugs called nucleoside analog reverse transcriptase inhibitors (such as zidovudine, also called AZT), which interrupt an early stage of virus replication; and the more recent protease inhibitors, which interrupt the same process at a later stage. These "cocktail" drug regimens are

188 not cures, and they typically cause unpleasant side effects such as nausea and

The diarrhea. However, when started early, they enable people infected with HIV to

Reproductive live relatively normal lives for longer periods.



In addition to CD4-cell counts of less than 200, AIDS is defined by the presence of one or more of 26 conditions, most of which are "opportunistic" infections that a healthy person could easily fight off. These include highly aggressive forms of certain cancers such as lymphomas (cancers of the immune system) and a type of skin cancer called Kaposi's sarcoma. Other opportunistic infections are:

• Pneumocystis carinii pneumonia (PCP)

• severe cytomegalovirus infection

• toxoplasmosis

• diarrhea caused by Cryptosporidium or Isospora organisms


• cryptococcosis

• chronic herpes simplex infection

People with opportunistic infections experience symptoms such as coughing, shortness of breath, seizures, severe and persistent diarrhea, fever, vision loss, severe headaches, weight loss, extreme fatigue, nausea, vomiting, lack of coordination, coma, abdominal cramps, difficult or painful swallowing, and mental changes such as confusion and forgetfulness.

In addition to treatment for such separate conditions, which can be very difficult to coordinate, adults with CD4-cell counts of less than 200 are given drug treatment to prevent the occurrence of PCP, which is one of the most common and deadly opportunistic infections associated with HIV Regardless of CD4-cell counts, people who survive PCP must take these drugs for the rest of their lives.

The course of AIDS varies widely. Many people with AIDS are so debilitated by their symptoms that they are unable to hold a job or perform simple household chores. Others may go through periods of devastating illness followed by periods of normal functioning.

Despite years of research, there is still no vaccine for AIDS. Thus the only way to prevent infection by HIV is to avoid behaviors that allow transmission of the virus. This means not using intravenous drugs, not sharing needles if you use intravenous drugs, and not using anyone else's toothbrush, razor, or other implements that could be contaminated with blood. Also, of course, it means practicing safer sex (see page 181). People who have a history of other STDs are more vulnerable to infection with HIV, and should be treated immediately for any STD they may acquire.

It is not necessary to avoid normal contact with people infected with HIV, even if they have developed full-blown AIDS. That's because HIV is not spread through casual contact, including contact with:

• food utensils and food

• towels and bedding

• swimming pools

• telephones

HIV also is not spread by hugging, holding hands, or having other physical contact in which neither blood nor semen is exchanged.

If you do have to come into contact with the blood of someone whom you have reason to suspect may be infected with HIV, or if you are infected and there is any possibility of getting your blood on someone else, you should wear latex gloves or take other protective measures.

Researchers around the world are working to develop HIV vaccines and new therapies for AIDS and its associated conditions. Some vaccines and many drugs are in the testing stage. At the same time, researchers are trying to determine exactly how HIV damages the immune system so they can more precisely target their efforts. Of special interest to researchers are the 50 or so persons known to have been infected with HIV more than 10 years ago who have never developed AIDS. Do they have a less virulent form of the virus? Or does something in their genetic makeup protect them from AIDS? The answers may point the way toward a vaccine or, perhaps someday, a cure.

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