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AIDS,or acquired immune deficiency syndrome, is the end stage of aninfectious disease caused by the human immunodeficiency virus, or HIV.There are two variants of the HIV virus, HIV-1 and HIV-2, both of whichultimately cause AIDS. The virusdamages the immune system, leaving the patient vulnerable to certaincancerous tumors and increasingly severe opportunistic infections. HIVcan be transmitted whenever a body fluid containing the virus--semen,saliva, blood, or breast milk--comes into contact with a mucousmembrane or the bloodstream itself. A person can get AIDSthrough sexual intercourse, anal or oral sex, childbirth,breastfeeding, blood transfusion, tattoos or body piercing, or sharinghypodermic needles.
Asof 2009, about 0.6 percent of the world's population is infected withHIV, or about 35 million people. Ninety-five percent of these cases arein Africa or southeastern Asia. About 25 million people have died of AIDSsince 1981, making the disease one of the deadliest pandemics inhistory. In the United States, the CDC's recently revised estimatesindicate that about 945,000 people have been diagnosed with AIDSsince 1981, and about 1.2 million are currently living with HIVinfection. About a quarter of these people are unaware that they areinfected with the virus. The CDC estimates that there are 56,300 newcases of HIV infection in the United States each year.
The CDC gives the following statistics for specific groups within the United States:
- Malesaccount for 74 percent of persons with HIV infection in the UnitedStates, although worldwide, the figure for males is 50 percent.
- Interms of race or ethnicity, 47 percent of persons with HIV infectionare African American, 34 percent are Caucasian, 17 percent areHispanic, and 2 percent are Native American or Asian American.
- Interms of method of transmission, 50 percent of infected persons are menwho had sex with men; 33 percent had high-risk heterosexual sex; 13percent are injection drug users; and the remainder are people whoengaged in more than one high-risk behavior.
- In terms of agegroup, 1 percent of infected persons are under 13 years of age; 15percent are between the ages of 13 and 24; 26 percent are between theages of 25 and 34; 32 percent are between the ages of 35 and 44; 20percent are between the ages of 45 and 54; 8 percent are 55 or older.
Aworrisome new trend as of 2009 is the return and increase of high-riskbehaviors among men who have sex with men in Canada and the UnitedStates. This trend appears to have been triggered by the spread ofmethamphetamine addiction from the West Coast to the Eastern Seaboardsince the early 2000s.
AIDS in women
Womenexposed to HIV infection through heterosexual contact are the mostrapidly growing risk group in the United States. The genderdemographics of HIV infection within the United States are changing,with women accounting for more new cases in 2009 than was the case in1999. The percentage of AIDS casesdiagnosed in American women has risen from 7% in 1985 to about 26% in2006, the last year for which data are available. According to the CDC,in 2006 approximately 278,400 women in the United States were livingwith HIV/AIDS. The rate was highestamong black women, who had 23 times as many cases as Caucasian womenand 4 times as many cases as Hispanic women. About 75% of these womencontracted HIV through high-risk heterosexual activity; almost all ofthe remainder acquired the infection through needle sharing.
Theprevalence of women with HIV in the United States is low, however,compared to the rate in many countries in the developing world.Worldwide about half the people living with HIV are women. According tothe United Nations, in 2005 about 59% of women living in sub-SaharanAfrica are infected with HIV. The vast majority of them were infectedthrough having unprotected sex with an infected male partner. Onetheory that has been proposed to explain the higher rate of AIDSin women in Africa is the prevalence of schistosomiasis in the region.Schistosomiasis is a parasitic disease caused by a trematode (a type offlatworm) that affects as many as 50% of women in some parts of Africa;while it is rarely fatal, schistosomiasis damages the tissues liningthe vagina, making them more vulnerable to the AIDS virus.
AIDS in children
Since AIDScan be transmitted from an infected mother to a fetus during pregnancyor to an infant during the birth process or through breastfeeding, allinfants born to HIV-positive mothers are considered a high-risk group.However, prenatal drug treatment of HIV-positive mothers in developedcountries has reduced the number of children born infected with HIV. Inthe developing world, drug treatment is either not available or notaffordable. According to the United Nations Children's Fund (UNICEF)worldwide 2.3 million children under age 13 were living with HIV in2006. The previous year, about 380,000 children died of AIDSand more than half a million children were newly infected. UNICEFestimates that at least 15 million children have lost at least oneparent to AIDS.
AIDSis the leading causes of death in children under age five in many partsof Africa and Southeast Asia. One reason for this tragedy is that only1% of sexually active women in these regions get tested for HIVinfection, and these women can become pregnant before they developsymptoms of the disease. The interval between exposure to HIV and thedevelopment of AIDS is shorter in children than in adults. Infants infected with HIV have a high chance of developing AIDS within one year and dying before age three. In the remainder, AIDS progresses more slowly; the average child patient survives to about seven years of age. Some survive into early adolescence.
AIDS in older adults
The demographics of HIV infection among the elderly have changed since the early days of the AIDS epidemic. In the mid-1980s, most cases of AIDSamong older adults in the United States were the result of transfusionswith contaminated blood. The introduction of effective screening testsfor blood products has virtually eliminated this path of HIVtransmission, however; as of 2009, almost all cases of AIDS in seniors are the result of sexual activity. In the United States, about 10 percent of all cases of AIDS occur in people over 50, and 3 percent in people over 60. About 35 percent of seniors who develop AIDSare homosexual or bisexual men; others are heterosexual men living inurban areas who engage in high-risk sex with prostitutes. In addition,the number of older adults with HIV/AIDS is rising; the CDC estimates that by 2015, half of all persons living with HIV/AIDS in North America will be over the age of 50.
Onereason that sexually active seniors are particularly at risk for HIVinfection is that they are rarely concerned about contraception. Adultsover 50 are five times more likely than younger people to haveunprotected sex because they think of condoms as a method of birthcontrol rather than a means of preventing disease transmission. Inaddition, older women have thinner and more fragile tissues lining thewalls of the vagina; these tissues are more likely to be bruised ordamaged during unprotected intercourse, making it easier for the virusto enter the underlying tissues. Several studies done in 2006 and 2007have reported that older women are less likely than their youngercounterparts to take precautions against HIV infection, in part becausethey are less sexually active than older men, and partly because theydo not perceive themselves as being at risk for HIV infection.
According to the Merck Manual of Geriatrics , "Practically no prevention information on AIDSis targeted at elderly persons, although most elderly persons aresexually active." According to statistics compiled by the Centers forDisease Control and Prevention, about 2100 men between the ages of 55and 59 are diagnosed with HIV infection each year, and 800 over the ageof 65. Since the epidemic began in 1981, 15,000 adults over age 65 havebeen diagnosed with HIV in the United States.
AIDSis now considered a pandemic because it has spread to every country inthe world. According to the World Health Organization (WHO), 34 millionpeople around the world were living with HIV infection in 2009; 2.1million people died in 2008 from the disease, 330,000 of them children.Scientists think that the virus that causes AIDSoriginated somewhere in the African rainforest as an infection ofchimpanzees and Old World monkeys. At some point in the twentiethcentury the virus jumped the species barrier from monkeys into humans,most likely somewhere in western Africa. The earliest known case of HIVinfection was found in a blood sample collected from a man in Kinshasain the Congo in 1959. AIDS was firstdefined as an epidemic human disease in June 1981 by the Centers forDisease Control and Prevention (CDC). The virus that causes AIDS was identified by two teams of French and American scientists in 1983-1984.
The first cases of AIDSin the United States were not diagnosed until 1981, when the CDCreported a cluster of five cases of an opportunistic lung infectionamong homosexual men in Los Angeles. In the first 15 years of theepidemic, there were no effective treatments for HIV infection (thereis still no cure as of 2009). In 1996, a team of researchers inCalifornia introduced a form of treatment known as highly activeantiretroviral therapy or HAART. While drug therapy is not a cure for AIDS, it can slow the progress of the disease and improve the patient's quality of life.
HIVinfection progresses in stages as the virus gradually weakens thebody's immune system. It takes an average of 11 years for HIV infectionto progress to AIDS, although the disease progresses faster in children and the elderly. AIDSis diagnosed when the count of certain white blood cells in thepatient's blood drops to a critical level or the patient developslife-threatening tumors or opportunistic infections.
In theearly stage of HIV infection, the patient may have no symptoms at allor a mild flu-like illness with fever and headache within a few days orweeks of getting infected. These symptoms usually go away withouttreatment and the person feels normal, even though they are a carrierand can transmit the infection to others. The infected person maycontinue to feel well for a period ranging from a few months to severalyears.
AIDS can be transmitted in several ways. The risk factors for HIV transmission vary according to the method of transmission.
- Sexualcontact. People at greatest risk are those who do not practice safersex by always using a condom, those who have multiple sexual partners,those who participate in anal intercourse, and those who have sex witha partner who has HIV infection and/or other sexually transmitteddiseases (STDs). In the United States and Europe, most cases ofsexually transmitted HIV infection result from homosexual contact,whereas in Africa, the disease is spread primarily through sexualintercourse among heterosexuals. Most people with AIDS in the United States are between 25 and 44 years of age.
- Transmissionin pregnancy. High-risk mothers include women sexually active withbisexual men, intravenous drug users, and women living in neighborhoodswith a high rate of HIV infection among heterosexuals. The chances oftransmitting the disease to the child are higher in women in advancedstages of the disease. Breast feeding increases the risk of HIVtransmission as HIV passes into breast milk. The rate of pediatric HIVtransmission in the United States had decreased substantially becauseof HIV testing and improved drug treatment for infected mothers, sofewer than 1% of AIDS cases now occur in children under age 15. In the developing world, mother to infant transmission remains epidemic. In 2006, AIDSwas the single most common cause of death in children under age 5 inSouth Africa, while worldwide children account for about 10% of all AIDS cases.
- Exposureto contaminated blood. Risk of HIV transmission among intravenous drugusers increases with the frequency and duration of intravenous use,frequency of needle sharing, number of people sharing a needle, and therate of HIV infection in the local population. In 2006, about 19% ofmen with AIDS and 25% of women with AIDScontracted the disease through sharing needles during intravenous druginjection. With the introduction of new blood product screening in themid-1980s, HIV transmission through blood transfusions became rare inthe developed world. However, contaminated blood is still a significantsource of infection in the developing world.
- Transmission via improperly sterilized tattooing or body piercing needles.
- Needlesticks or body fluid splashes among health care professionals.Transmission through theses sources accounts for fewer than 0.3% of allHIV infections in the United States. This rate reflects the emphasis onuniversal safety precautions (e.g., use of gloves, face shields, properdisposal of needles) among health care professionals and firstresponders.
Some older adults are at higher risk thanothers of HIV infection. In order to determine whether HIV testingshould be a personal priority, an adult 55 years of age or older shoulduse the following checklist of high-risk behaviors for 1978 and later:
- Shared needles for injecting drugs or steroids.
- If a male, had unprotected sex with other males.
- Had unprotected sex with someone known or suspected to be infected with HIV.
- Had a blood transfusion between 1978 and 1985.
- Had another sexually transmitted disease.
- Had unprotected sex with anyone with any of the five previous risk factors.
Causes and symptoms
The cause of AIDSis infection with human immunodeficiency virus or HIV. HIV is aretrovirus that reproduces by inserting its own genetic material into atype of white blood cell called a CD4 lymphocyte. When the virus copiesbreak out of the infected white blood cell, they attack other CD4 cellsand the cycle repeats. The virus has a short life cycle, needing aslittle as 1.5 days to enter a cell, replicate, and release new copiesof itself to infect other cells. Eventually so many of the white bloodcells have been destroyed that the body's immune system is weakened andthe person can no longer fight off opportunistic infections. Thepatient may also develop certain cancers associated with a weakenedimmune system.
Thesymptoms of HIV infection vary according to the progress of theinfection. As mentioned above, about 30 percent of patients develop anacute syndrome resembling flu within a month of exposure to HIV. Thepatient typically has a fever, headache, swollen lymph nodes, andfatigue. This illness is called acute retroviral syndrome or ARS. Thesymptoms then disappear; however, the infected person is highlycontagious in this early phase and can readily pass on the virus toothers. The patient may or may not have developed antibodies to HIV (aprocess known as seroconversion) at this point; thus a test for HIVinfection in this early period may not yield positive results eventhough the patient is in fact infected.
In the second phase, thevirus may be silent, but more commonly it produces complications.Patients in this stage of infection may have the following symptoms:
- Swelling of the lymph nodes that lasts three months or longer.
- Fevers and night sweats.
- Loss of energy.
- Weight loss.
- Frequent yeast infections of the vagina or mouth and throat. Yeast infections of the mouth are sometimes called thrush.
- Skin rashes or flaky skin that does not go away.
- Short-termmemory loss. This symptom helps to explain why HIV infection in seniorsis often misdiagnosed as early-stage Alzheimer's.
In full-blown AIDS,the person develops one or more of the following opportunisticinfections. Death usually results from one of these infections or froman AIDS-related cancer.
- Lung infections: these include a type of pneumonia caused by an organism known as Pneumocystis jirovecii , a yeast-like fungus; and tuberculosis.
- Mouth infections: these include oral candidiasis, or thrush.
- Infectionsof the digestive tract: these include parasitic as well as bacterialinfections, and are often marked by severe diarrhea.
- Infections of the central nervous system: these include meningitis and toxoplasmosis. AIDSdementia complex (ADC), which is often misdiagnosed as Alzheimer'sdisease, is caused by destruction of brain tissue by toxins secreted byHIV. AIDS dementia complex affects between 10 and 20 percent of AIDS patients in the United States and is often the first symptom of full-blown AIDS.Like Alzheimer's, ADC is characterized by memory loss, inability toconcentrate, loss of motor ability, poor balance, and mood changes.
AIDS-relatedcancers include Kaposi's sarcoma, a skin cancer occasionally found inolder men who do not have HIV infection; and cervical cancers in women.AIDS patients are also at increased risk of developing Hodgkin's disease, Burkitt's lymphoma, and cancers of the anus or rectum.
Posted By: adminThursday, June 17, 2010 Total views: 4310|