AIDS is the most severe form of disease caused by HIV (human immunodeficiency virus), a virus that damages the immune system, leaving a person open to many life-threatening infections.
KEYWORDS
for searching the Internet and other reference sourcesEpidemic
HAART
Immunodeficiency
Infection
Protease inhibitors
Retrovirus
Virology
How Did the AIDS Epidemic Begin?
In the early 1980s, doctors in New York and California began noticing a very unusual disease in a small number of young men. The men, who were mostly homosexual, were developing unusual infections and cancers, and some of them were dying. The infections were similar to those seen in children who are born with very weak immune systems. But these men had been healthy as children and should have had normal immune systems.Government scientists searched for other cases of the disease, and found more and more of them. The disease also seemed to strike people who had received blood transfusions, and drug addicts who had shared needles with each other. Reports of the disease began to come in from other countries, including African and Caribbean countries, where it seemed to spread mainly by sexual contact between men and women. Some babies were born with it, too.
AIDS
Less than 20 years later, that mysterious disease had become one of the worst epidemics ever to strike humanity. AIDS (acquired immune deficiency syndrome) had killed almost 14 million people worldwide, including more than 3 million children, by the end of 1998. In the United States, AIDS had killed more than 400,000 people, including almost 5,000 children younger than age 15.HIV
Even greater numbers of people are infected with the virus that causes AIDS, but have not yet developed the disease. In the United States, almost a million people are thought to be infected with HIV, the human immunodeficiency virus, and most do not know they are carrying the virus that causes AIDS. Within 10 years of becoming infected, about half of them will have developed AIDS. Worldwide, more than 33 million people are living with HIV infection, mostly in developing countries in Africa and Asia.People at risk
Like other sexually transmitted diseases, HIV infection is a particular risk among teenagers and young adults. In the United States, more than 110,000 people in their twenties have been diagnosed with AIDS, and it is likely that most of them became infected with HIV when they were teenagers. It is estimated that up to one quarter of all HIV infections in the United States—and half of all HIV infections worldwide—occur in teenagers and people in their early twenties.Many billions of dollars have been spent to understand HIV/AIDS, to prevent it, and to treat it. Although there is still no cure and no proven vaccine, there has been progress. Because of new drugs, the number of deaths from AIDS fell sharply in the United States starting in 1996. Many Americans infected with HIV are living longer and better lives: they are going to school, working, raising their families, and enjoying life. There is hope that in the United States, HIV will soon be similar to other chronic * diseases, like diabetes or asthma: a serious disease, but one that is manageable with good medical care.
*
chronic
(KRON-ik) means continuing for a long period of time.
But in most other parts of the world, treatment is far too expensive for
people with HIV and AIDS, and the epidemic is growing worse each year.
Developing nations in Africa, Asia, the Caribbean, and South America have
been hit hard. In some parts of Africa, the virus has infected a quarter
of all adults and is reversing years of struggle to improve living
conditions. Life expectancy is falling, and infant mortality (the infant
death rate) is rising.
AIDS, and the infections that occur in the disorder, can affect many
parts of the body.
Even in the United States, it is estimated that 40,000 people a year are
still getting infected with HIV and, unless treatment improves, it still
appears that almost all HIV-infected people will eventually die of AIDS.
Carl's Family: How Could This Happen?
When Carl's mother told him she had HIV, he could not believe it. After all, she worked full time, kept house, volunteered at church, and was raising two kids alone. She was the last person in the world he could imagine shooting up drugs. And in the eight years since Carl's father had died of a brain tumor, she had not been out on a date, let alone had relationships with men. How could she have caught HIV?But Carl, now 15, found out that he had not been told the full story of his father's death. Yes, it had been cancer, but it was a kind of cancer—lymphoma of the brain—that is much more common in HIV-infected people. Carl's father had died of AIDS.
"I didn't know it until your father got sick," his mother said, "but when he was a teenager, your age, he got into drugs. He and his friends injected cocaine and heroin. After a couple of years, he stopped, he got his life together, and he even went to college. By the time he met me, he thought that other life was all behind him."
By the time Carl's father realized he had HIV in his body, he was already very sick. And he had already infected Carl's mother. Although a mother can pass HIV to her baby, neither Carl nor his sister was born infected. "It was just luck," his mother said. But Carl did not feel lucky.
How Does HIV Spread?
HIV infection can spread only when an infected person's body fluid (blood, semen, vaginal fluid, breast milk, or any body fluid containing blood) enters the bloodstream or contacts the mucous membrane * of another person.Sexual intercourse, either homosexual (between men) or heterosexual (between men and women), is responsible for most cases of HIV infection. The virus also commonly spreads among people who share contaminated needles when they inject drugs. Infected mothers may pass it on to their babies during pregnancy, childbirth, or breast-feeding.
If blood is infected, transfusions can spread HIV. But in the United States, blood transfusions have been tested for HIV since 1985, and the risk of infection from a transfusion is extremely low.
Oral sex also can spread the virus, and at least one case has been reported in which the virus is thought to have spread through wet kissing (French kissing).
*
mucous membrane
is the kind of tissue that lines body openings, such as the mouth,
vagina, and rectum, as well as the respiratory, intestinal, and genital
tracts.
HIV does not spread through air, water, food, or objects like doorknobs or
toilet seats. It is not spread by mosquitoes or by other insects. A person
cannot "catch HIV" by playing with, going to school with,
shaking hands with, hugging, or even living with an infected person.
Fortunately, HIV is much less contagious than many other infections,
including chickenpox, flu, or hepatitis B.
How Can HIV Infection Be Prevented?
Prevention of HIV infection is easy—and hard. People can completely protect themselves by never sharing needles, whether for drug use or such practices as tattooing or body piercing, and by avoiding all sexual contact. As people grow up and become sexually active, however, things become more difficult.Safer sex
The safest sexual relationship is between two uninfected people who have sex only with each other, sometimes called a monogamous (mo-NA-ga-mus), mutually faithful relationship. But there is no sure way to tell if a person is infected or not. People with HIV may seem completely healthy and often do not know they are infected. In the first few months after infection, they may even test negative on HIV tests.So if people are sexually active, how can they reduce their chances of infection? One important step is not to have sexual contact with anyone who may be at risk of HIV infection. Who is at risk? Anyone who ever shared needles or engaged in promiscuous sex (had many sexual partners), as well as anyone who ever had a sexual partner who shared needles or engaged in promiscuous sex. Of course, often people are not truthful about past behavior. To judge whether a potential sexual partner is being honest, or is at risk, it may help to know the person well, over a long period of time. Unfortunately, however, that, too, is no guarantee.
Other safety measures
Other steps to reduce the chances of infection include:- using latex condoms correctly and consistently during sexual activity
- not engaging in anal sex or other sexual practices likely to cause breaks in the skin
- not having sexual relations with multiple sexual partners
- avoiding drugs and alcohol, since their use might prevent people from making good decisions about protecting themselves and others from HIV
- getting prompt treatment for any sore or blister in the genital area, since these can act as an open door for HIV to enter the body.
The U.S. and the World
The HIV/AIDS epidemic presents a very different picture in the United States and in the developing nations of the world, where 95 percent of all cases occur.- Worldwide, more than 75 percent of all infections in adults result from sex between men and women. In the United States, male-female sex accounts for less than 20 percent of infections, although this percentage has been increasing. Instead, most U.S. infections result from sex between men orfrom needle-sharing by drug users. The reason forthis difference is not clear.
- Worldwide, the death toll of 13.9 million continues to rise. An estimated 2.5 million people died of AIDS in 1998 alone, including more than 500,000 children, most of whom had been infected before or at birth. But in the United States, the death toll started falling in the late 1990s. From 1996 to 1997, for instance, it fell from 37,525 to 21,909.
- Worldwide, about 1 in every 100 adults (ages 15 to 49) is infected. But in more than a dozen African nations, more than 10 in 100 people are infected. In some nations, including Botswana and Zimbabwe, more than 20 in 100 people have HIV. In the United States, the overall infection rate is about 1 in 200.
- Worldwide, the epidemic has created more than 8 million "AIDS orphans," childrenyoungerthan age 15 who have lost their mother or both parents to the disease. Ninety-five percent of them live in Africa. Less than half of 1 percent (about 45,000) live in the United States.
- Worldwide, the number of children with AIDS continues to grow as more infected mothers pass on the virus to their babies. But in the United States, the number of children with AIDS fell in the late 1990s because treatment of mothers prevented the virus from spreading to their babies.
What Does HIV Do in the Body?
Once HIV gets into the body, it attacks and enters white blood cells called CD4 helper lymphocytes (LIM-fo-sites). These cells are very important for the proper functioning of the immune system. When the virus begins to destroy CD4 cells more rapidly than the body can replace them, the immune system becomes so weak that severe infections and cancers can develop. The virus also can directly attack some organs, including the brain, the kidneys, and the heart.
The retrovirus HIV invades a body cell called a CD4 helper
lymphocyte. Once inside the lymphocyte, HIV combines its genetic
material with the CD4 cell's genetic material. After that,
whenever the CD4 cell reproduces itself, it also reproduces
HIV. HIV
can destroy CD4 lymphocytes and spread throughout the body during
active AIDS infections.
HIV is a special kind of virus called a retrovirus (see sidebar) and
includes two species, or types. HIV-1, which is far more common and more
severe, has caused the current epidemic. Different subtypes of it occur in
different parts of the world. HIV-2, which is seen in some parts of West
Africa, causes a milder version of AIDS.
One reason it has been impossible so far to find an HIV cure or vaccine is that the virus can mutate and change its genetic features with amazing speed. That means HIV can quickly grow resistant to a medicine, making the drug no longer effective. It also means that any drug or vaccine must be able to work against a wide range of different strains of HIV.
What Are the Symptoms?
HIV Infection
Between two and four weeks after people get infected, most people develop a flu-like illness with fever, sore throat, muscle aches, and (often) a rash that looks a little like measles. After two weeks, this illness usually disappears. Others, however, get infected with no initial symptoms of illness. A person can transmit HIV to others without having had any symptoms.Over the next few years, a person may suffer fevers, swollen glands, fatigue, weight loss, and diarrhea. These symptoms generally occur long before the serious complications that come with AIDS. Some people may have minor infections such as thrush (a yeast infection of the mouth) or shingles (a skin infection caused by the virus that causes chickenpox). Others do not have any symptoms until they develop AIDS itself.
Children, especially those who were infected before they were born, generally develop symptoms more quickly than adults. Often they are sick from birth or may fail to grow and develop at a normal rate.
AIDS
AIDS is often heralded by infections or cancers that occur only in people whose immune systems have become very weak. Some of the most common are:- Pneumocystis carinii (nu-mo-SIS-tis ka-RIN-ee) pneumonia (PCP), the most common complication of AIDS in the United States since the epidemic began. It causes fever, cough, and shortness of breath.
- Cerebral toxoplasmosis (tok-so-plaz-MO-sis), which can destroy parts of the brain. It usually begins with a headache and often paralyzes one side of the body.
- Cryptococcal meningitis (krip-to-KOK-al menin-JI-tis), an infection of the brain and of the meninges, which is the membrane lining the central nervous system. It begins with fever and headache, and it can cause coma.
- Intestinal infections caused by parasites such as cryptosporidiosis (krip-to-spo-rid-e-O-sis) or isosporiasis (i-sos-po-RY-a-sis).
- Eye infections caused by cytomegalovirus, which can cause blindness.
- Infections caused by bacteria called Mycobacterium avium, which resemble tuberculosis.
- Cancers, including Kaposi's sarcoma (which causes purplish skin nodules), lymphoma (which may affect any organ, especially the brain and intestinal tract), and invasive cervical cancer (a genitaltract cancer in women).
- AIDS dementia, in which people have difficulty thinking, remembering, and concentrating.
- In addition, many common infections (such as syphilis and ordinary pneumonia) are more common or more severe in people with AIDS. The most striking example is tuberculosis, which is 100 times more likely to cause illness in a person who has HIV than in an uninfected person.
.jpg)
0 comments