人教版高中英语选修6 UNIT 3 A HEALTHY LIFE PERIOD 3 素材（4） .doc

1、AIDSAcquired immunodeficiency syndrome (AIDS)Classification and external resourcesThe is a symbol for solidarity with HIV-positive people and those living with AIDS.-List of abbreviations used in this articleAIDS: Acquired immune deficiency syndromeHIV: CD4+: CCR5: CDC: WHO: PCP: TB: MTCT: Mother-to

2、-child transmissionHAART: STI/STD: /diseaseAcquired immune deficiency syndrome or acquired immunodeficiency syndrome (AIDS) is a disease of the human caused by the (HIV).This condition progressively reduces the effectiveness of the immune system and leaves individuals susceptible to and . HIV is thr

3、ough direct contact of a or the bloodstream with a containing HIV, such as , , , , and .This transmission can involve , or , , contaminated , exchange between mother and baby during , , or , or other exposure to one of the above bodily fluids.AIDS is now a . In 2007, it was estimated that 33.2millio

4、n people lived with the disease worldwide, and that AIDS had killed an estimated 2.1million people, including 330,000 children. Over three-quarters of these deaths occurred in , retarding and destroying . indicates that HIV originated in west-central Africa during the late nineteenth or early twenti

5、eth century. AIDS was first recognized by the U.S. in 1981 and its cause, HIV, identified in the early 1980s.Although treatments for AIDS and HIV can slow the course of the disease, there is currently no vaccine or cure. treatment reduces both the and the morbidity of HIV infection, but these drugs

6、are expensive and routine access to antiretroviral is not available in all countries. Due to the difficulty in treating HIV infection, preventing infection is a key aim in controlling the AIDS epidemic, with health organizations promoting and in attempts to slow the spread of the virus.SymptomsA gen

7、eralized graph of the relationship between HIV copies (viral load) and CD4 counts over the average course of untreated HIV infection; any particular individuals disease course may vary considerably. CD4+ T Lymphocyte count (cells/mm) HIV RNA copies per mL of plasmaThe symptoms of AIDS are primarily

8、the result of conditions that do not normally develop in individuals with healthy . Most of these conditions are infections caused by , , and that are normally controlled by the elements of the immune system that HIV damages. are common in people with AIDS. HIV affects nearly every .People with AIDS

9、 also have an increased risk of developing various cancers such as , and cancers of the immune system known as . Additionally, people with AIDS often have systemic symptoms of infection like , (particularly at night), swollen glands, chills, weakness, and . The specific opportunistic infections that

10、 AIDS patients develop depend in part on the prevalence of these infections in the geographic area in which the patient lives.Main symptoms of AIDS.Pulmonary infectionsX-ray of . There is increased white (opacity) in the lower lungs on both sides, characteristic of PCP (originally known as Pneumocys

11、tis carinii pneumonia, and still abbreviated as PCP, which now stands for Pneumocystis pneumonia) is relatively rare in healthy, people, but common among HIV-infected individuals. It is caused by .Before the advent of effective diagnosis, treatment and routine in Western countries, it was a common i

12、mmediate cause of death. In developing countries, it is still one of the first indications of AIDS in untested individuals, although it does not generally occur unless the CD4 count is less than 200 cells per L of blood. (TB) is unique among infections associated with HIV because it is transmissible

13、 to immunocompetent people via the respiratory route, is easily treatable once identified, may occur in early-stage HIV disease, and is preventable with drug therapy. However, is a potentially serious problem.Even though its incidence has declined because of the use of directly observed therapy and

14、other improved practices in Western countries, this is not the case in developing countries where HIV is most prevalent. In early-stage HIV infection (CD4 count 300 cells per L), TB typically presents as a pulmonary disease. In advanced HIV infection, TB often presents atypically with extrapulmonary

15、 (systemic) disease a common feature. Symptoms are usually constitutional and are not localized to one particular site, often affecting , , urinary and , , regional , and the .Gastrointestinal infections is an inflammation of the lining of the lower end of the (gullet or swallowing tube leading to t

16、he ). In HIV infected individuals, this is normally due to fungal () or viral ( or ) infections. In rare cases, it could be due to .Unexplained chronic in HIV infection is due to many possible causes, including common bacterial (, , or ) and parasitic infections; and uncommon opportunistic infection

17、s such as , , complex (MAC) and viruses, , , and , (the latter as a course of ).In some cases, diarrhea may be a side effect of several drugs used to treat HIV, or it may simply accompany HIV infection, particularly during primary HIV infection. It may also be a side effect of used to treat bacteria

18、l causes of diarrhea (common for ). In the later stages of HIV infection, diarrhea is thought to be a reflection of changes in the way the absorbs nutrients, and may be an important component of HIV-related .Neurological and psychiatric involvementHIV infection may lead to a variety of neuropsychiat

19、ric , either by infection of the now susceptible nervous system by organisms, or as a direct consequence of the illness itself. is a disease caused by the single-celled called Toxoplasma gondii; it usually infects the brain, causing toxoplasma , but it can also infect and cause disease in the and lu

20、ngs. Cryptococcal meningitis is an infection of the (the membrane covering the brain and ) by the fungus . It can cause fevers, , , , and . Patients may also develop and confusion; left untreated, it can be lethal. (PML) is a , in which the gradual destruction of the sheath covering the of nerve cel

21、ls impairs the transmission of nerve impulses. It is caused by a virus called which occurs in 70% of the population in form, causing disease only when the immune system has been severely weakened, as is the case for AIDS patients. It progresses rapidly, usually causing death within months of diagnos

22、is. (ADC) is a metabolic induced by HIV infection and fueled by immune activation of HIV infected brain and . These cells are productively infected by HIV and secrete of both host and viral origin. Specific neurological impairments are manifested by cognitive, behavioral, and motor abnormalities tha

23、t occur after years of HIV infection and are associated with low CD4+ T cell levels and high plasma viral loads.Prevalence is 1020% in Western countries but only 12% of HIV infections in India. This difference is possibly due to the HIV subtype in India. AIDS related mania is sometimes seen in patie

24、nts with advanced HIV illness; it presents with more irritability and cognitive impairment and less euphoria than a associated with true . Unlike the latter condition, it may have a more chronic course. This syndrome is less often seen with the advent of multi-drug therapy.Tumors and malignanciesPat

25、ients with HIV infection have substantially increased incidence of several . This is primarily due to co-infection with an , especially (EBV), (KSHV), and human (HPV).Kaposis sarcoma (KS) is the most common tumor in HIV-infected patients. The appearance of this tumor in young homosexual men in 1981

26、was one of the first signals of the AIDS epidemic. Caused by a virus called (KSHV), it often appears as purplish on the skin, but can affect other organs, especially the , gastrointestinal tract, and lungs.High-grade such as , Burkitts-like lymphoma, diffuse large B-cell lymphoma (DLBCL), and presen

27、t more often in HIV-infected patients. These particular cancers often foreshadow a poor prognosis. In some cases these lymphomas are AIDS-defining. (EBV) or KSHV cause many of these lymphomas. in HIV-infected women is considered AIDS-defining. It is caused by (HPV).In addition to the AIDS-defining t

28、umors listed above, HIV-infected patients are at increased risk of certain other tumors, such as and and . However, the incidence of many common tumors, such as or , does not increase in HIV-infected patients. In areas where is extensively used to treat AIDS, the incidence of many AIDS-related malig

29、nancies has decreased, but at the same time malignant cancers overall have become the most common cause of death of HIV-infected patients.Other opportunistic infectionsAIDS patients often develop opportunistic infections that present with non-specific symptoms, especially and weight loss. These incl

30、ude infection with -intracellulare and (CMV). CMV can cause colitis, as described above, and can cause . due to is now the third most common opportunistic infection (after extrapulmonary tuberculosis and ) in HIV-positive individuals within the endemic area of .CauseFor more details on this topic, s

31、ee . of HIV-1, colored green, budding from a cultured .AIDS is the most severe acceleration of with HIV. HIV is a that primarily infects vital organs of the human such as (a subset of ), and . It directly and indirectly destroys CD4+ T cells.Once HIV has killed so many CD4+ T cells that there are fe

32、wer than 200 of these cells per (L) of , is lost. HIV infection progresses over time to clinical latent HIV infection and then to early HIV infection and later to AIDS, which is identified either on the basis of the amount of CD4+ T cells remaining in the blood, and/or the presence of certain infect

33、ions, as noted above.In the absence of , the is nine to ten years, and the median survival time after developing AIDS is only 9.2 months. However, the rate of clinical disease progression varies widely between individuals, from two weeks up to 20years.Many factors affect the rate of progression. The

34、se include factors that influence the bodys ability to defend against HIV such as the infected persons general immune function. Older people have weaker immune systems, and therefore have a greater risk of rapid disease progression than younger people.Poor access to and the existence of coexisting i

35、nfections such as also may predispose people to faster disease progression. The infected persons plays an important role and some people are to certain strains of HIV. An example of this is people with the variation are resistant to infection with certain of HIV. HIV is genetically variable and exis

36、ts as different strains, which cause different rates of clinical disease progression.Sexual transmissionSexual transmission occurs with the contact between sexual secretions of one person with the rectal, genital or oral of another. Unprotected receptive sexual acts are riskier than unprotected inse

37、rtive sexual acts, and the risk for transmitting HIV through unprotected anal intercourse is greater than the risk from vaginal intercourse or oral sex.However, oral sex is not entirely safe, as HIV can be transmitted through both insertive and receptive oral sex. greatly increases the risk of HIV t

38、ransmission as condoms are rarely employed and physical trauma to the vagina occurs frequently, facilitating the transmission of HIV.Other (STI) increase the risk of HIV transmission and infection, because they cause the disruption of the normal barrier by and/or microulceration; and by accumulation

39、 of pools of HIV-susceptible or HIV-infected cells ( and ) in semen and vaginal secretions. Epidemiological studies from sub-Saharan Africa, and suggest that genital ulcers, such as those caused by and/or , increase the risk of becoming infected with HIV by about fourfold. There is also a significan

40、t although lesser increase in risk from STIs such as , and , which all cause local accumulations of lymphocytes and macrophages.Transmission of HIV depends on the infectiousness of the and the susceptibility of the uninfected partner. Infectivity seems to vary during the course of illness and is not

41、 constant between individuals. An undetectable plasma does not necessarily indicate a low viral load in the seminal liquid or genital secretions.However, each 10-fold increase in the level of HIV in the blood is associated with an 81% increased rate of HIV transmission. Women are more susceptible to

42、 HIV-1 infection due to hormonal changes, vaginal microbial ecology and physiology, and a higher prevalence of sexually transmitted diseases.People who have been infected with one strain of HIV can still be infected later on in their lives by other, more strains.Infection is unlikely in a single enc

43、ounter. High rates of infection have been linked to a pattern of overlapping long-term sexual relationships. This allows the virus to quickly spread to multiple partners who in turn infect their partners. A pattern of serial monogamy or occasional casual encounters is associated with lower rates of

44、infection.HIV spreads readily through heterosexual sex in Africa, but less so elsewhere. One possibility being researched is that , which affects up to 50 per cent of women in parts of Africa, damages the lining of the vagina.Exposure to blood-borne pathogensCDC poster from 1989 highlighting the thr

45、eat of AIDS associated with drug useThis transmission route is particularly relevant to users, and recipients of and blood products. Sharing and reusing contaminated with HIV-infected blood represents a major risk for infection with HIV.Needle sharing is the cause of one third of all new HIV-infecti

46、ons in , China, and . The risk of being infected with HIV from a single prick with a needle that has been used on an HIV-infected person is thought to be about 1 in 150 (). with anti-HIV drugs can further reduce this risk.This route can also affect people who give and receive and . are frequently no

47、t followed in both sub-Saharan Africa and much of Asia because of both a shortage of supplies and inadequate training.The estimates that approximately 2.5% of all HIV infections in sub-Saharan Africa are transmitted through unsafe healthcare injections. Because of this, the has urged the nations of

48、the world to implement precautions to prevent HIV transmission by health workers.The risk of transmitting HIV to recipients is extremely low in developed countries where improved donor selection and HIV screening is performed. However, according to the , the overwhelming majority of the worlds popul

49、ation does not have access to safe blood and between 5% and 10% of the worlds HIV infections come from transfusion of infected blood and blood products.Perinatal transmissionThe transmission of the virus from the mother to the child can occur during the last weeks of pregnancy and at childbirth. In

50、the absence of treatment, the transmission rate between a mother and her child during pregnancy, labor and delivery is 25%.However, when the mother takes antiretroviral therapy and gives birth by , the rate of transmission is just 1%. The risk of infection is influenced by the viral load of the moth

51、er at birth, with the higher the viral load, the higher the risk. also increases the risk of transmission by about 4%.MisconceptionsMain article: A number of misconceptions have arisen surrounding HIV/AIDS. Three of the most common are that AIDS can spread through casual contact, that sexual interco

52、urse with a virgin will cure AIDS, and that HIV can infect only homosexual men and drug users. Other misconceptions are that any act of anal intercourse between gay men can lead to AIDS infection, and that open discussion of homosexuality and HIV in schools will lead to increased rates of homosexual

53、ity and AIDS.PathophysiologyThis section may require to meet Wikipedias . Please if you can. (April 2008)The pathophysiology of AIDS is complex, as is the case with all . Ultimately, HIV causes AIDS by depleting CD4+ T helper lymphocytes. This weakens the immune system and allows . T lymphocytes are

54、 essential to the immune response and without them, the body cannot fight infections or kill cancerous cells. The mechanism of CD4+ T cell depletion differs in the acute and chronic phases.During the acute phase, HIV-induced cell lysis and killing of infected cells by accounts for CD4+ T cell deplet

55、ion, although may also be a factor. During the chronic phase, the consequences of generalized immune activation coupled with the gradual loss of the ability of the immune system to generate new T cells appear to account for the slow decline in CD4+ T cell numbers.Although the symptoms of immune defi

56、ciency characteristic of AIDS do not appear for years after a person is infected, the bulk of CD4+ T cell loss occurs during the first weeks of infection, especially in the intestinal mucosa, which harbors the majority of the lymphocytes found in the body. The reason for the preferential loss of muc

57、osal CD4+ T cells is that a majority of mucosal CD4+ T cells express the CCR5 coreceptor, whereas a small fraction of CD4+ T cells in the bloodstream do so.HIV seeks out and destroys CCR5 expressing CD4+ cells during acute infection. A vigorous immune response eventually controls the infection and i

58、nitiates the clinically latent phase. However, CD4+ T cells in mucosal tissues remain depleted throughout the infection, although enough remain to initially ward off life-threatening infections.Continuous HIV replication results in a state of generalized immune activation persisting throughout the c

59、hronic phase. Immune activation, which is reflected by the increased activation state of immune cells and release of proinflammatory , results from the activity of several HIV gene products and the immune response to ongoing HIV replication. Another cause is the breakdown of the immune surveillance

60、system of the mucosal barrier caused by the depletion of mucosal CD4+ T cells during the acute phase of disease.This results in the systemic exposure of the immune system to microbial components of the guts normal flora, which in a healthy person is kept in check by the mucosal immune system. The ac

61、tivation and proliferation of T cells that results from immune activation provides fresh targets for HIV infection. However, direct killing by HIV alone cannot account for the observed depletion of CD4+ T cells since only 0.01-0.10% of CD4+ T cells in the blood are infected.A major cause of CD4+ T c

62、ell loss appears to result from their heightened susceptibility to apoptosis when the immune system remains activated. Although new T cells are continuously produced by the to replace the ones lost, the regenerative capacity of the thymus is slowly destroyed by direct infection of its by HIV. Eventu

63、ally, the minimal number of CD4+ T cells necessary to maintain a sufficient immune response is lost, leading to AIDSCells affectedThe , entering through which ever route, acts primarily on the following cells: : o CD4+ o o o Certain cells : o of the nervous system o o o - indirectly by the action of

64、 and the The effectThe has but how it does it is still not quite clear. It can remain inactive in these cells for long periods, though. This effect is hypothesized to be due to the CD4-gp120 interaction. The most prominent effect of the HIV virus is its T-helper cell suppression and lysis. The cell

65、is simply killed off or deranged to the point of being function-less (they do not respond to foreign ). The infected B-cells can not produce enough antibodies either. Thus the immune system collapses leading to the familiar AIDS complications, like infections and neoplasms (vide supra). Infection of

66、 the cells of the CNS cause acute , subacute , vacuolar myelopathy and . Later it leads to even complex. The CD4-gp120 interaction (see above) is also permissive to other viruses like , , virus, etc. These viruses lead to further cell damage i.e. cytopathy. Molecular basisFor details, see: Diagnosis

67、The diagnosis of AIDS in a person infected with HIV is based on the presence of certain signs or symptoms. Since June 5, 1981, many definitions have been developed for surveillance such as the and the . However, clinical staging of patients was not an intended use for these systems as they are neith

68、er sensitive, nor specific. In developing countries, the staging system for HIV infection and disease, using clinical and laboratory data, is used and in developed countries, the (CDC) Classification System is used.WHO disease staging systemMain article: In 1990, the (WHO) grouped these infections a

69、nd conditions together by introducing a staging system for patients infected with HIV-1. An update took place in September 2005. Most of these conditions are that are easily treatable in healthy people. Stage I: HIV infection is and not categorized as AIDS Stage II: includes minor manifestations and

70、 recurrent infections Stage III: includes unexplained for longer than a month, severe bacterial infections and tuberculosis Stage IV: includes of the , of the , , or and ; these diseases are indicators of AIDS. CDC classification systemMain article: There are two main definitions for AIDS, both prod

71、uced by the (CDC). The older definition is to referring to AIDS using the diseases that were associated with it, for example, , the disease after which the discoverers of HIV originally named the virus. In 1993, the CDC expanded their definition of AIDS to include all HIV positive people with a CD4+

72、 T cell count below 200 per L of blood or 14% of all . The majority of new AIDS cases in use either this definition or the pre-1993 CDC definition. The AIDS diagnosis still stands even if, after treatment, the CD4+ T cell count rises to above 200 per L of blood or other AIDS-defining illnesses are c

73、ured.HIV testMain article: Many people are unaware that they are infected with HIV. Less than 1% of the sexually active urban population in Africa has been tested, and this proportion is even lower in rural populations. Furthermore, only 0.5% of pregnant women attending urban health facilities are c

74、ounseled, tested or receive their test results. Again, this proportion is even lower in rural health facilities. Therefore, and blood products used in medicine and medical research are screened for HIV.HIV tests are usually performed on venous blood. Many laboratories use fourth generation screening

75、 tests which detect anti-HIV antibody (IgG and IgM) and the HIV p24 antigen. The detection of HIV antibody or antigen in a patient previously known to be negative is evidence of HIV infection. Individuals whose first specimen indicates evidence of HIV infection will have a repeat test on a second bl

76、ood sample to confirm the results.The (the time between initial infection and the development of detectable antibodies against the infection) can vary since it can take 36months to and to test positive. Detection of the virus using polymerase chain reaction () during the window period is possible, a

77、nd evidence suggests that an infection may often be detected earlier than when using a fourth generation EIA screening test.Positive results obtained by PCR are confirmed by antibody tests. Routinely used HIV tests for infection in , born to HIV-positive mothers, have no value because of the presenc

78、e of maternal antibody to HIV in the childs blood. HIV infection can only be diagnosed by PCR, testing for HIV pro-viral DNA in the childrens .PreventionEstimated per act risk for acquisitionof HIV by exposure routeExposure RouteEstimated infectionsper 10,000 exposuresto an infected sourceBlood Tran

79、sfusion9,000Childbirth2,500Needle-sharing injection drug use67Percutaneous needle stick30Receptive anal intercourse*50Insertive anal intercourse*6.5Receptive penile-vaginal intercourse*10Insertive penile-vaginal intercourse*5Receptive oral intercourse*1Insertive oral intercourse*0.5* assuming no con

80、dom use source refers to oral intercourseperformed on a manThe three main transmission routes of HIV are , exposure to infected body fluids or tissues, and from mother to or child during period. It is possible to find HIV in the , , and of infected individuals, but there are no recorded cases of inf

81、ection by these secretions, and the risk of infection is negligible.Sexual contactThe majority of HIV infections are acquired through relations between partners, one of whom has HIV. The primary mode of HIV infection worldwide is through sexual contact between members of the opposite sex.During a se

82、xual act, only male or female can reduce the chances of infection with HIV and other STDs and the chances of becoming . The best evidence to date indicates that typical condom use reduces the risk of HIV transmission by approximately 80% over the long-term, though the benefit is likely to be higher

83、if condoms are used correctly on every occasion.The male condom, if used correctly without oil-based lubricants, is the single most effective available technology to reduce the sexual transmission of HIV and other sexually transmitted infections. Manufacturers recommend that oil-based lubricants suc

84、h as , butter, and not be used with latex condoms, because they dissolve the , making the condoms . If necessary, manufacturers recommend using -based lubricants.Oil-based lubricants can however be used with condoms.The is an alternative to the male condom and is made from , which allows it to be us

85、ed in the presence of oil-based lubricants. They are larger than male condoms and have a stiffened ring-shaped opening, and are designed to be inserted into the vagina.The female condom contains an inner ring, which keeps the condom in place inside the vagina inserting the female condom requires squ

86、eezing this ring. However, at present availability of female condoms is very low and the price remains prohibitive for many women.Preliminary studies suggest that, where female condoms are available, overall protected sexual acts increase relative to unprotected sexual acts, making them an important

87、 HIV prevention strategy.Studies on couples where one partner is infected show that with consistent condom use, HIV infection rates for the uninfected partner are below 1% per year. Prevention strategies are well-known in developed countries, but epidemiological and behavioral studies in Europe and

88、North America suggest that a substantial minority of young people continue to engage in high-risk practices despite HIV/AIDS knowledge, underestimating their own risk of becoming infected with HIV. have shown that male lowers the risk of HIV infection among heterosexual men by up to 60%. It is expec

89、ted that this procedure will be actively promoted in many of the countries affected by HIV, although doing so will involve confronting a number of practical, cultural and attitudinal issues.Some experts fear that a lower perception of vulnerability among circumcised men may result in more sexual ris

90、k-taking behavior, thus negating its preventive effects. However, one randomized controlled trial indicated that adult male circumcision was not associated with increased HIV risk behavior.Exposure to infected body fluidsHealth care workers can reduce exposure to HIV by employing precautions to redu

91、ce the risk of exposure to contaminated blood. These precautions include barriers such as gloves, masks, protective eyeware or shields, and gowns or aprons which prevent exposure of the skin or mucous membranes to blood borne pathogens. Frequent and thorough washing of the skin immediately after bei

92、ng contaminated with blood or other bodily fluids can reduce the chance of infection. Finally, sharp objects like needles, scalpels and glass, are carefully disposed of to prevent needlestick injuries with contaminated items. Since intravenous drug use is an important factor in HIV transmission in d

93、eveloped countries, strategies such as are used in attempts to reduce the infections caused by drug abuse.Mother-to-child transmission (MTCT)Current recommendations state that when replacement feeding is acceptable, feasible, affordable, sustainable and safe, HIV-infected mothers should avoid breast

94、-feeding their infant. However, if this is not the case, exclusive breast-feeding is recommended during the first months of life and discontinued as soon as possible. It should be noted that women may breastfeed other children who are not their own; see .TreatmentSee also and . a nucleoside analog r

95、everse transcriptase inhibitor (NARTI or NRTI)The chemical structure of AbacavirThere is currently no or cure for or AIDS. The only known methods of prevention are based on avoiding exposure to the virus or, failing that, an antiretroviral treatment directly after a highly significant exposure, call

96、ed (PEP). PEP has a very demanding four week schedule of dosage. It also has very unpleasant side effects including , , and .Antiviral therapyCurrent treatment for HIV infection consists of , or HAART. This has been highly beneficial to many HIV-infected individuals since its introduction in 1996 wh

97、en the protease inhibitor-based HAART initially became available. Current optimal HAART options consist of combinations (or cocktails) consisting of at least three drugs belonging to at least two types, or classes, of agents. Typical regimens consist of two (NARTIs or NRTIs) plus either a or a (NNRT

98、I). Because HIV disease progression in children is more rapid than in adults, and laboratory parameters are less predictive of risk for disease progression, particularly for young infants, treatment recommendations are more aggressive for children than for adults. In developed countries where HAART

99、is available, doctors assess the , rapidity in CD4 decline, and patient readiness while deciding when to recommend initiating treatment.Standard goals of HAART include improvement in the patients quality of life, reduction in complications, and reduction of HIV viremia below the limit of detection,

100、but it does not cure the patient of HIV nor does it prevent the return, once treatment is stopped, of high blood levels of HIV, often HAART resistant. Moreover, it would take more than the lifetime of an individual to be cleared of HIV infection using HAART. Despite this, many HIV-infected individua

101、ls have experienced remarkable improvements in their general health and quality of life, which has led to the plummeting of HIV-associated morbidity and mortality. In the absence of HAART, progression from HIV infection to AIDS occurs at a of between nine to ten years and the median survival time af

102、ter developing AIDS is only 9.2months. HAART is thought to increase survival time by between 4 and 12years.For some patients, which can be more than fifty percent of patients, HAART achieves far less than optimal results, due to medication intolerance/side effects, prior ineffective antiretroviral t

103、herapy and infection with a drug-resistant strain of HIV. Non-adherence and non-persistence with therapy are the major reasons why some people do not benefit from HAART. The reasons for non-adherence and non-persistence are varied. Major psychosocial issues include poor access to medical care, inade

104、quate social supports, psychiatric disease and drug abuse. HAART regimens can also be complex and thus hard to follow, with large numbers of pills taken frequently. Side effects can also deter people from persisting with HAART, these include , , , , an increase in risks and . Anti-retroviral drugs a

105、re expensive, and the majority of the worlds infected individuals do not have access to medications and treatments for HIV and AIDS.Experimental and proposed treatmentsIt has been postulated that only a vaccine can halt the pandemic because a vaccine would possibly cost less, thus being affordable f

106、or developing countries, and would not require daily treatments. However, even after almost 30years of research, HIV-1 remains a difficult target for a vaccine.Research to improve current treatments includes decreasing side effects of current drugs, further simplifying drug regimens to improve adher

107、ence, and determining the best sequence of regimens to manage drug resistance. A number of studies have shown that measures to prevent opportunistic infections can be beneficial when treating patients with HIV infection or AIDS. against A and B is advised for patients who are not infected with these

108、 viruses and are at risk of becoming infected. Patients with substantial immunosuppression are also advised to receive prophylactic therapy for (PCP), and many patients may benefit from prophylactic therapy for and as well.Researchers have discovered an that can destroy the protein CD4 binding site.

109、 This protein is common to all HIV variants as it is the attachment point for and subsequent compromising of the immune system.In , , a 42-year-old patient infected with HIV for more than a decade was given an experimental with cells that contained an unusual natural variant of the cell-surface rece

110、ptor. This variant has been shown to make some cells from people who are born with it resistant to infection with some strains of HIV. Almost two years after the transplant, and even after the patient reportedly stopped taking antiretroviral medications, HIV has not been detected in the patients blo

111、od. Alternative medicineVarious forms of have been used to treat symptoms or alter the course of the disease. Current studies indicate that alternative medicine therapies have little effect on the mortality or morbidity of the disease, but may improve the quality of life of individuals with AIDS. Th

112、e psychological benefits of these therapies are the most important use. has been used to alleviate some symptoms with no success and cannot cure the HIV infection. Several randomized clinical trials testing the effect of herbal medicines have shown that there is no evidence that these herbs have any

113、 effect on the progression of the disease, but may instead produce serious side-effects.Morbidity and mortality among HIV-infected adults with adequate dietary nutritional intake is unaffected by supplementation. A large Tanzanian trial in immunologically- and nutritionally-compromised pregnant and

114、lactating women showed a number of benefits to daily multivitamin supplementation for both mothers and children. Dietary intake of micronutrients at levels by HIV-infected adults is recommended by the . There is some evidence that supplementation in children reduces mortality and improves growth. Da

115、ily doses of can suppress HIV viral burden with an associated improvement of the CD4 count. Selenium can be used as an adjunct therapy to standard antiviral treatments, but cannot itself reduce mortality and morbidity.PrognosisWithout treatment, the net median survival time after infection with HIV

116、is estimated to be 9 to 11 years, depending on the HIV subtype, and the median survival rate after diagnosis of AIDS in resource-limited settings where treatment is not available ranges between 6 and 19 months, depending on the study. In areas where it is widely available, the development of as effe

117、ctive therapy for HIV infection and AIDS reduced the death rate from this disease by 80%, and raised the life expectancy for a newly diagnosed HIV-infected person to about 20 years.As new treatments continue to be developed and because HIV continues to resistance to treatments, estimates of survival

118、 time are likely to continue to change. Without antiretroviral therapy, death normally occurs within a year. Most patients die from opportunistic infections or associated with the progressive failure of the immune system. The rate of clinical disease progression varies widely between individuals and

119、 has been shown to be affected by many factors such as host susceptibility and immune function health care and co-infections, as well as which particular strain of the virus is involved.EpidemiologyMain article: This article may need to be updated. Please update this article to reflect recent events

120、 or newly available information, and remove this template when finished. Please see the for more information.Estimated prevalence of HIV among young adults (15-49) per country at the end of 2005The AIDS pandemic can also be seen as several epidemics of separate subtypes; the major factors in its spr

121、ead are sexual transmission and vertical transmission from mother to child at birth and through breast milk. Despite recent, improved access to antiretroviral treatment and care in many regions of the world, the AIDS pandemic claimed an estimated 2.1million (range 1.92.4million) lives in 2007 of whi

122、ch an estimated 330,000 were children under 15years. Globally, an estimated 33.2million people lived with HIV in 2007, including 2.5million children. An estimated 2.5 million (range 1.84.1million) people were newly infected in 2007, including 420,000 children. remains by far the worst affected regio

123、n. In 2007 it contained an estimated 68% of all people living with AIDS and 76% of all AIDS deaths, with 1.7million new infections bringing the number of people living with HIV to 22.5million, and with 11.4million AIDS orphans living in the region. Unlike other regions, most people living with HIV i

124、n sub-Saharan Africa in 2007 (61%) were women. Adult in 2007 was an estimated 5.0%, and AIDS continued to be the single largest cause of mortality in this region. has the largest population of HIV patients in the world, followed by and India. are second worst affected; in 2007 this region contained

125、an estimated 18% of all people living with AIDS, and an estimated 300,000 deaths from AIDS. India has an estimated 2.5million infections and an estimated adult prevalence of 0.36%. has fallen dramatically in the worst-affected countries; for example, in 2006 it was estimated that it had dropped from

126、 65 to 35 years in .HistoryMain article: AIDS was first reported June 5, 1981, when the U.S. recorded a cluster of (now still classified as PCP but known to be caused by ) in five homosexual men in . In the beginning, the CDC did not have an official name for the disease, often referring to it by wa

127、y of the diseases that were associated with it, for example, , the disease after which the discoverers of HIV originally named the virus. They also used Kaposis Sarcoma and Opportunistic Infections, the name by which a task force had been set up in 1981. In the general press, the term GRID, which st

128、ood for , had been coined. The CDC, in search of a name, and looking at the infected communities coined “the 4H disease,” as it seemed to single out , , , and users. However, after determining that AIDS was not isolated to the community, the term GRID became misleading and AIDS was introduced at a m

129、eeting in July 1982. By September 1982 the CDC started using the name AIDS, and properly defined the illness.A more controversial theory known as the suggests that the AIDS epidemic was inadvertently started in the late 1950s in the by s research into a . According to , this scenario is not supporte

130、d by the available evidence.A recent study states that HIV probably moved from to and then entered the United States around 1969.Society and cultureStigma became a poster child for HIV after being expelled from school because of his infection.AIDS stigma exists around the world in a variety of ways,

131、 including , , and avoidance of HIV infected people; compulsory HIV testing without prior or protection of ; violence against HIV infected individuals or people who are perceived to be infected with HIV; and the of HIV infected individuals. Stigma-related violence or the fear of violence prevents ma

132、ny people from seeking HIV testing, returning for their results, or securing treatment, possibly turning what could be a manageable chronic illness into a death sentence and perpetuating the spread of HIV.AIDS stigma has been further divided into the following three categories: Instrumental AIDS sti

133、gmaa reflection of the fear and apprehension that are likely to be associated with any deadly and transmissible illness. Symbolic AIDS stigmathe use of HIV/AIDS to express attitudes toward the social groups or lifestyles perceived to be associated with the disease. Courtesy AIDS stigmastigmatization

134、 of people connected to the issue of HIV/AIDS or HIV- positive people. Often, AIDS stigma is expressed in conjunction with one or more other stigmas, particularly those associated with , , , , and .In many , there is an association between AIDS and homosexuality or bisexuality, and this association

135、is correlated with higher levels of sexual prejudice such as attitudes. There is also a perceived association between AIDS and all male-male sexual behavior, including sex between uninfected men.Economic impactMain article: Changes in life expectancy in some hard-hit African countries. Botswana Zimb

136、abwe Kenya South Africa UgandaHIV and AIDS affects by reducing the availability of . Without proper , health care and medicine that is available in developed countries, large numbers of people suffer and die from AIDS-related complications. They will not only be unable to work, but will also require

137、 significant medical care. The forecast is that this will probably cause a collapse of economies and societies in countries with a significant AIDS population. In some heavily infected areas, the epidemic has left behind many cared for by elderly .The increased mortality in this region will result i

138、n a and . This smaller will be predominantly young people, with reduced knowledge and leading to reduced productivity. An increase in workers time off to look after sick family members or for will also lower productivity. Increased mortality will also weaken the mechanisms that generate human capita

139、l and in people, through loss of and the death of parents. By killing off mainly young adults, AIDS seriously weakens the population, reducing the resources available for such as education and health services not related to AIDS resulting in increasing pressure for the states finances and slower gro

140、wth of the economy. This results in a slower growth of the tax base, an effect that will be reinforced if there are growing expenditures on treating the sick, training (to replace sick workers), sick pay and caring for AIDS orphans. This is especially true if the sharp increase in adult mortality sh

141、ifts the responsibility and blame from the family to the government in caring for these orphans.On the level of the household, AIDS results in both the loss of income and increased spending on healthcare by the household. The income effects of this lead to spending reduction as well as a substitutio

142、n effect away from education and towards healthcare and funeral spending. A study in showed that households with an HIV/AIDS patient spent twice as much on medical expenses as other households.Religion and AIDSThe topic of has become highly controversial in the past twenty years, primarily because m

143、any prominent religious leaders have publicly declared their opposition to the use of contraception, which scientists feel is currently the only means to stop the epidemic. Other issues involve religious participation in global health care services and collaboration with secular organizations such a

144、s UNAIDS and the World Health Organization.AIDS denialismMain article: A small number of activists question the connection between HIV and AIDS, the existence of HIV, or the validity of current treatment methods (even going so far as to claim that the drug therapy itself was the cause of AIDS deaths

145、). Though these claims have been examined and thoroughly rejected by the , they continue to be promulgated through the and have had a significant political impact. In , former President embrace of AIDS denialism resulted in an ineffective governmental response to the AIDS epidemic that has been blam

146、ed for hundreds of thousands of AIDS-related deaths.Active pursuit of HIV infectionMain article: A subculture of desire and actively pursue HIV infection by seeking partners who are HIV-positive and voluntarily having unprotected intercourse with them. In terms, those who seek infection are called a

147、nd those who infect them are called . This phenomenon should be distinguished from , which is the preference for unprotected intercourse without the active desire for HIV infection.The exact extent of practice remains largely unknown. Not all those who self-identify as part of this subculture are actually intent on spreading HIV. Some bugchasers try to connect with giftgivers via the Internet. Other bugchasers organize and participate in bug parties or conversion parties, sex parties where HIV positive and negative men engage in unprotected sex, in hopes of acquiring HIV (getting the gift).