AIDS (Acquired Immune Deficiency Syndrome )

AIDS is the final, life-threatening stage of infection with human immunodeficiency virus (HIV). AIDS stands for acquired immune deficiency syndrome. The name refers to the fact that HIV severely damages the immune system, the body's most important defence against disease. Cases of AIDS were first identified in 1981, in the United States, but researchers have detected HIV in a specimen collected in 1959 in central Africa. Millions of AIDS cases have been diagnosed worldwide. 

AIDS virus in a white blood cell 
How AIDS affect the body : AIDS is caused by two viruses that belong to a group called retroviruses. The first AIDS virus was isolated by researchers in France in 1983 and in the United States in 1984. The virus became known as HIV-1. In 1985, scientists in France identified another closely related virus that also produces AIDS. This virus, named HIV-2, occurs mainly in Africa. HIV-1 occurs throughout the world. 

HIV infects certain white blood cells, including T-helper cells and macrophages, that play key roles in the immune system. The virus attaches to CD4 receptor molecules on the surface of these cells, which are often called CD4 cells. HIV enters CD4 cells and inserts its own genes into the cell's reproductive system. The cell then produces more HIV, which spreads to other CD4 cells. Eventually infected cells die. 

Symptoms. People infected with HIV eventually develop symptoms that may be caused by other, less serious conditions. With HIV infection, however, these symptoms are prolonged and often more severe. They include enlarged lymph glands, tiredness, fever, loss of appetite and weight, diarrhoea, yeast infections of the mouth and vagina, and night sweats. 

HIV commonly causes a severe "wasting syndrome," resulting in substantial weight loss, a general decline in health, and eventual death. In many patients, the virus infects the brain and nervous system, and may cause dementia, a condition characterized by sensory, thinking, or memory disorders. HIV infection of the brain may also cause movement or coordination problems. 

Opportunistic infections. HIV makes infected people susceptible to illnesses that do not normally occur or that are normally not serious. These infections are called opportunistic because they take advantage of damage to the immune system. With the onset of an opportunistic infection or one of several other severe illnesses or with a marked decline in the number of CD4 cells, an HIV-infected person is considered to have AIDS. 

There are many opportunistic illnesses that typically affect AIDS patients. In North America and Europe, Pneumocystis carinii pneumonia, yeast infections of the oesophagus (tube that carries food to the stomach), cytomegalovirus retinitis, Kaposi's sarcoma, and tuberculosis are the most common. People with AIDS may contract several of these diseases. 

Pneumocystis carinii pneumonia, which is an infection of the lungs, is the leading cause of death among AIDS patients. Yeast infections of the oesophagus cause severe pain when swallowing and result in weight loss and dehydration. Cytomegalovirus retinitis is an eye infection that can cause blindness. Kaposi's sarcoma is a form of cancer that usually arises in the skin. The tumours may look like bruises, but they grow. 

Another illness that defines AIDS in HIV-infected people is tuberculosis. For many decades, the number of cases of tuberculosis in the United States declined. However, in the mid-1980's, doctors noticed a growing number of cases of tuberculosis in HIV patients. People with HIV are especially vulnerable to tuberculosis because of their damaged immune systems. 

An HIV-infected person may develop AIDS from 2 to 15 or more years after becoming infected. In children born with HIV infection, this interval is usually shorter. Medical treatment can increase the interval by inhibiting the growth of HIV, preserving the immune system, and delaying the onset of opportunistic illnesses. A few people who have been infected with HIV for more than 12 years have not developed any symptoms or suffer only minor symptoms. Others have symptoms of HIV infection but none of the opportunistic illnesses. An infected person can transmit the virus to another person whether or not symptoms are present. Infection with HIV appears to be lifelong in all who become infected. 

How HIV is transmitted 

Researchers have identified three ways in which HIV is transmitted: (1) sexual intercourse, (2) direct contact with infected blood, and (3) transmission from an infected woman to her fetus or baby. The most common way of becoming infected is through intimate sexual contact with an HIV-infected person. HIV is transmitted through all forms of sexual intercourse, including genital, anal, and oral sex. 

People who inject drugs into their bodies can be exposed to infected blood by sharing hypodermic needles, syringes, or equipment used to prepare drugs for injection. In the past, transfusion and transplant recipients and people with haemophilia contracted the virus from the blood, blood components, tissues, or organs of infected donors. However, screening and testing of both donated blood and potential organ donors have virtually eliminated this hazard. Medical workers can become infected with HIV by coming into direct contact with infected blood. This may occur through injury with a needle or other sharp instrument used in treating an HIV-infected patient. A few patients became infected while receiving treatment from an HIV-infected American dentist and from a French surgeon. 

An infected pregnant woman can transmit the AIDS virus to her fetus even if she has no symptoms. Transmission may also occur from an HIV-infected mother to her baby through breast-feeding. 

Studies indicate that HIV is not transmitted through air, food, or water, or by insects. No known cases of AIDS have resulted from sharing kitchens or utensils, bathrooms, locker rooms, shower rooms, living space, or classrooms. 

Medical care for HIV infection and AIDS 

Diagnosis. Tests for detecting evidence of HIV-1 in the blood became widely available in 1985. The tests for detecting HIV-2 became widely available in 1992. HIV tests determine the presence of antibodies to the AIDS virus. Antibodies are proteins produced by certain white blood cells to react with specific viruses, bacteria, or foreign substances that enter the body. The presence of antibodies to HIV indicates infection with the virus. 

Tests that directly measure the amount of HIV in the blood have been developed. These tests enable doctors to predict the future health of with HIV and estimate their survival time. In 1996, the first home tests for HIV became available in the United States. People send in a dried blood spot by post, then use an identification number to learn results confidentially by telephone. 

People with HIV infection are diagnosed as having AIDS when tests indicate that they have fewer than 200 CD4 cells per microlitre (0.000001 litre) of blood or when they develop one or more opportunistic illnesses. All HIV-infected patients should have their health closely monitored by a doctor, and receive periodic blood tests to measure the levels of virus and CD4 cells in their blood. 

Treatments have been developed, but no cure for HIV infection or AIDS has yet been found. Scientists have worked to understand how HIV infects and damages human cells since AIDS was identified. In one important discovery, researchers learned that HIV uses an enzyme called reverse transcriptase to reproduce in CD4 cells. Because this enzyme is not normally found in human cells, scientists focused on developing drugs that block its action. These efforts led to development of a class of antiviral drugs called reverse transcriptase inhibitors. The first of these drugs was zidovudine, commonly known as AZT. 

AZT and other reverse transcriptase inhibitors produce toxic side effects, including severe anaemia that requires blood transfusions. HIV also develops resistance to these drugs when they are given singly. Doctors combine the drugs and vary the order in which they are given to improve their effectiveness. 

In 1995 and 1996, the first three protease inhibitors--indinavir, ritonavir, and saquinavir--were approved for treating HIV. These antiviral drugs block the action of protease, another HIV enzyme not found in human cells. Protease inhibitors block a later step in HIV reproduction than do reverse transcriptase inhibitors. 

In 1996, several studies showed that certain combinations of anti-viral drugs could decrease HIV in the blood to undetectable levels. Although HIV appears to persist inside CD4 cells, the studies raised hope that combination therapy can control reproduction of the virus. The research also raised hope for an eventual cure. But the drugs must be taken in large quantities for a long time, and HIV may develop resistance to them. Doctors need to determine which combinations of drugs are safest and most effective over the long term. 

Doctors also prevent and treat opportunistic infections in AIDS patients. Pneumocystis carinii pneumonia can be prevented with specific antibiotics. Doctors use biological substances called interferons to treat Kaposi's sarcoma. Researchers believe any eventual cure for AIDS must stop the growth of the virus, prevent opportunistic illnesses, and restore normal function to the immune system. 

Prevention. To prevent transmission of HIV, sexual contact with anyone who is or might be infected with the virus must be avoided. The most effective preventive strategies are to refrain from all sexual intimacy or restrict sexual intimacy to one uninfected person. Health authorities have recommended that a condom be used every time sexual intercourse occurs with a person who is infected with HIV or whose infection status is unknown. Drug users should never share hypodermic needles, syringes, or other injection equipment. Research has shown that AZT reduces the risk of transmission from an infected woman to her fetus or baby. Doctors administer AZT and other anti-viral drugs to HIV-infected women during pregnancy and labour, and to their newborn babies. Doctors advise HIV-infected women not to breast-feed their infants. 

The tests to detect evidence of HIV-1 are used to screen all blood donated in many countries. These tests have greatly increased the safety of transfusions. Screening for HIV-2 began in 1992. 

There are guidelines for preventing the transmission of HIV in treatment and care centres. Doctors, dentists, and other medical workers now wear gloves, masks, and other protective clothing during many examinations and procedures. 

Researchers are working to develop safe, effective, and economical vaccines against HIV infection. However, even if HIV transmission were to stop, AIDS cases would still occur for many years. This is because millions of people worldwide are already infected with the virus and have yet to develop the disease. As a result, scientists are attempting to develop vaccines to boost the immune systems of people infected with HIV. 

Social issues 

AIDS is a relatively new disease that involves sex and drugs and mainly affects young adults. For these reasons, it has generated widespread social concern. Some efforts to deal with AIDS or to prevent HIV transmission have provoked controversy. 

Education. Educating people about AIDS has become the chief approach to preventing infection. Some schools have set up health clinics that distribute condoms to students. However, some people oppose classroom discussion of condom use because they feel it implies acceptance of sexual intimacy outside of marriage. 

Preventing drug abuse and educating drug users about AIDS are important approaches to controlling HIV infection. Efforts to educate drug users include health and sex education as well as needle and syringe exchange programmes. However, these types of programmes have been criticized as seeming to imply acceptance of drug use. 

In many countries, national and local governments have provided funds for AIDS education, treatment, and research. Public health clinics offer counselling and HIV-antibody testing to people who have symptoms or are at risk of infection. In addition, these clinics may privately and confidentially notify an infected person's sexual or needle-sharing partners of their risk. Once notified, they, too, can receive preventive counselling, testing, and medical services. 

Public awareness. Many individuals and organizations, ranging from community-based groups to the Red Cross, have worked to increase public awareness of AIDS. They hope that greater awareness will result in more compassion and support for people with AIDS and adequate funding for AIDS prevention, research, and treatment. 

Celebrities have helped raise public consciousness of AIDS. Many well-known people have participated in education and fund-raising efforts. The epidemic also has gained attention as a result of several well-known people becoming infected with HIV or dying from AIDS. These people include the actor Rock Hudson, who died of AIDS in 1985; the tennis champion Arthur Ashe, who died in 1993; and the ballet dancer Rudolf Nureyev, who died in 1993. 

The World Health Organization (WHO), an agency of the United Nations that monitors the AIDS epidemic, has designated December 1 as World AIDS Day. Public agencies and schools around the world sponsor prevention programmes. Many individuals wear a red ribbon to show support for people with AIDS. 

Discrimination. Some people infected with HIV have unjustly lost or been denied jobs, housing, medical care, and health insurance. Children with AIDS have been kept from attending school. To prevent discrimination, many countries include AIDS patients and people infected with HIV under laws protecting the rights of people with disabilities. 

Preventing discrimination against AIDS patients is important not only for moral reasons but also to help maintain public health. When people are not afraid of discrimination, they are more likely to seek counselling and be tested for HIV infection. In many cases, this leads to less risky behaviour and earlier diagnosis. 

AIDS around the world 

Almost every nation has reported cases of AIDS. By the end of 1996, UNAIDS, the United Nations organization dealing with AIDS, estimated that there were 22.6 million people worldwide living with HIV infection or AIDS. Of these, 830,000 were children, with men accounting for 58 per cent and women 42 per cent of the remainder. Some 90 per cent of adults with HIV infection or AIDS were living in the developing world. India had the highest number of infections in the world, at over 3 million. This figure, however, represented less than 1 per cent of India's population. In some African countries in the region south of the Sahara, over 10 per cent of all adults were reported to be infected with HIV. 

By 1998 an estimated 30 million people worldwide were infected with HIV, 26 million of them residing in Africa, where more than 90 per cent of all AIDS deaths have also occurred. In some African countries, the epidemic had severely eroded population growth and life expectancy. Life expectancy had dropped from 66 years to 48 in Kenya, and from 62 to 41 in Botswana. In Zimbabwe, where every fifth adult was infected and more than 100 people a day were dying from AIDS, life expectancy was only 31 years. The Zimbabwean National Aids Coordination Programme (NACP) estimated that of the 1.5 million Zimbabweans who were infected with HIV, 35,000 had developed AIDS. 

In Africa, India, and Southeast Asia, transmission of HIV has occurred mostly among heterosexual men and women. In Africa, the spread of the virus has been accelerated by mass population movement resulting from poverty, war, and drought. In Asia, prostitution and intravenous drug use are major factors in the AIDS problem. Public health departments in many developing countries lack the resources to treat patients properly and to control the epidemic through education. Research has shown that the low social status of women in some countries contributes to the spread of AIDS, as women are unable to question their husbands' extra-marital sexual activities or to insist on using condoms. 

History of AIDS 

Scientists are not certain how, when, or where the AIDS virus evolved and first infected humans. Researchers have shown that HIV-1 and HIV-2 are more closely related to simian immunodeficiency viruses, which infect monkeys, than to each other. Thus, it has been suggested that HIV evolved from viruses that originally infected monkeys in Africa and was somehow transmitted to people. 

Scientists believe HIV infection became widespread after significant social changes took place in Africa during the 1960's and 1970's. Large numbers of people moved from rural areas to cities, resulting in crowding, unemployment, and prostitution. These conditions brought about an increase in cases of sexually transmitted diseases, including AIDS. HIV may have been introduced into industrial nations several times before transmission was sustained and became widespread. 

AIDS was first identified as a "new" disease by doctors in Los Angeles and New York City in 1980 and 1981. The doctors recognized the condition as something new because all the patients were previously healthy, young homosexual men suffering from otherwise rare forms of cancer and pneumonia. The name AIDS was adopted in 1982. Scientists soon determined that AIDS occurred when the immune system became damaged, and that the agent that caused the damage was spread through sexual contact, shared drug needles, and infected blood transfusions. 

After HIV was isolated as the cause of AIDS in 1983 and 1984, researchers developed tests to detect HIV infection. These tests have also been used to analyse stored tissues from several people who died of undetermined causes from the late 1950's to the 1970's. Scientists have concluded that some of these people died from AIDS. 

Efforts to control the spread of AIDS have had some success. For example, among homosexual men in the United States, HIV infection is spreading more slowly than it did in the early 1980's. This is due entirely to education about prevention and the resulting changes in sexual behaviour, such as decreased numbers of sexual partners and increased use of condoms. HIV blood tests, which became available in 1985, caused a gradual decline in transfusion-related cases in the late 1980's. The rate of AIDS in other groups rose, however, during the 1980's. These groups include heterosexual men and women, children born to HIV-infected women, people who inject drugs, and younger homosexual men. In October 1998, the National Center for Health Statistics (NCHS) reported that AIDS deaths in the United States dropped 47 per cent from 1996 to 1997.

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