Despite the overwhelming evidence that HIV causes AIDS, a hardcore group still denies it . We explore five of the most common myths about AIDS.

    MYTH: AIDS is not caused by HIV

    DEBUNKING: This is the biggie, of course. As long ago as 1983, researchers first isolated HIV from people with AIDS. By 1985, they had developed a test showing that the overwhelming majority of people with AIDS have antibodies to HIV in their blood. They also showed that people who test HIV-positive and initially appear healthy go on to develop AIDS the vast majority of the time unless they are treated.

    Denialists often claim that HIV has never met "Koch's postulates" - a list of conditions that must be met to prove that a particular infectious agent causes a disease, drawn up by 19th-century German scientist Robert Koch. It is debatable how appropriate it is to focus on a set of principles devised for bacterial infections in a century when viruses had not yet been discovered. HIV does, however, meet Koch's postulates as long as they are not applied in a ridiculously stringent way:

    POSTULATE 1:The germ must be found in every person with the disease. In 1993, the US Centers for Disease Control and Prevention in Atlanta, Georgia, reviewed 230,179 cases of AIDS-like illness. Only 47 people tested HIV-negative, less than 0.025 per cent.

    POSTULATE 2:The germ must be isolated from someone who has the disease and then grown in pure culture. HIV has been isolated according to the most rigorous standards of modern virology. A small group of Australian scientists, the so-called Perth Group, claims that there is no proof that HIV exists. Then again, neither do the viruses causing influenza, smallpox, yellow fever, measles and many others, according to their bizarre criteria.

    POSTULATE 3:The germ must cause the disease if given to a healthy person. Obviously no one is going to deliberately inject someone with HIV, but in three separate incidents, US laboratory workers accidentally exposed to purified HIV tested positive for that specific strain and later developed AIDS.

    MYTH: Antiretroviral drugs are "poisons"

    DEBUNKING: It is true that antiretroviral therapies （ART） cause side effects in many. These range from nausea and strange dreams to ones that can be life-threatening if not competently managed, such as nerve damage. Some are temporary while others persist.

    Side effects are less of a problem, however, for people in the west using the latest ART regimens. And whether the regimen is old or new, scores of clinical trials conducted on four continents have shown that the benefits far outweigh the risks. To take just one example, a study of 1255 patients over two years found that the death rate fell from 29 per cent per year to just under 9 per cent per year （The New England Journal of Medicine, vol 338, p 853）.

    MYTH: HIV tests are flawed

    DEBUNKING: The two most common HIV tests, ELISA and western blot, both test for HIV antibodies. The ELISA test used to occasionally generate false positives, for example by cross-reacting to flu antibodies if someone had recently had a flu vaccine. However, this has not been a problem since the test was improved in the mid-1990s. Plus people are only diagnosed as HIV-positive after an ELISA test has been confirmed by the western blot, which is more expensive and complicated but more accurate. The result is that less than 1 in 1000 tests now produces a false positive.

    MYTH: AIDS is caused by poverty or malnutrition

    DEBUNKING: This is often trotted out to explain the high toll of AIDS in Africa. In a study conducted in the Rakai district of Uganda, nearly 20,000 adults were followed for three years. The highest rate of HIV-related death was among the better educated and government employees, in other words, among the middle classes, rather than among the poor.

    Even in South Africa, for several years the heartland of denialism, the figures refute the poverty myth. A count of death certificates in South Africa found that 57 per cent more people died in 2002 than in 1997. Poverty and malnutrition in South Africa were not increasing over this period - and the government itself says poverty actually fell.

    MYTH: The lack of a widespread HIV epidemic in the west proves the orthodoxy is wrong

    DEBUNKING: In the early 1980s there were doom-laden predictions that HIV would spread from high-risk groups such as gay men and drug users to the general population. In sub-Saharan Africa, HIV is indeed rampant among heterosexuals, with rates among adults in South Africa, for example, as high as 18 per cent. Yet in the west and in many developing countries outside of Africa, HIV remains largely confined to certain groups.

    Why HIV spreads through some populations and not others is highly contentious. One theory is that the strain of HIV common in Africa is more easily spread by vaginal sex, while the strains outside Africa are more easily spread by anal sex.

    A different explanation is the "concurrency theory". It states that in African countries where there is a heterosexual HIV epidemic, it is more common for people to have two or more long-term sexual partners concurrently, which promotes the spread of the virus. Western heterosexuals, by contrast, are generally more likely to be serial monogamists. While they could have more partners over their lifetimes, those who contract HIV keep it trapped in a single relationship for months or years.

    盡管有著非常有說服力的證據(jù)表明HIV是引發(fā)AIDS的原因，一個中堅科研小組仍然否定了它。（見否認AIDS:致命的誤解 ）.我們發(fā)現(xiàn)了關于AIDS的五個最常見的不解之謎。

    不解之謎：AIDS不是由HIV病毒引起的

    解密：當然這是最大的誤解。早在1983年，研究人員們就首次從艾滋病患者身上分離出HIV病毒。到1985年，研究者們已經(jīng)證實絕大多數(shù)艾滋病患者的血液中存在HIV抗體。他們還指出，那些HIV病毒測試呈陽性的患者，即使最初看起來很健康，但如果不及時進行救治，不久就會患上艾滋病。

    反對者們的理由是HIV并不滿足"科赫基本原理"--19世紀德國科學家羅伯特·科赫提出的這項原理列舉了一系列要證明某種疾病是由某種病原體引發(fā)所需的必要條件。那個世紀病毒還未被發(fā)現(xiàn)，用判斷細菌感染的一系列標準來判斷艾滋病是否合適本身就是件值得爭議的事。況且，如果不是以一種嚴格到可笑程度的標準衡量，HIV還大體滿足科赫基本原理。

    原理1:必須在每位患病者身上都發(fā)現(xiàn)此種病菌。1993年，位于喬治亞州亞特蘭大的美國疾病預防控制中心回顧了230179例疑似艾滋病病例。只有47人HIV病毒測試呈陰性，這一比例低于0.025%.

    原理2:病菌必需從患病者身上獲得并在無菌環(huán)境下培養(yǎng)。HIV病毒的獲取是依照現(xiàn)代濾過性微生物學最嚴格的標準執(zhí)行。然而一小組名為帕斯小組（Perth Group）的澳大利亞科學家聲稱沒有證據(jù)表明HIV病毒存在。而且，依照他們奇異的標準，引起流感，天花，黃熱病，麻疹還有許多其他疾病的病毒也都不存在。

    原理3:如果將該病菌注入健康人體內，會引發(fā)健康人患上相應疾病。很顯然沒人愿意故意注射帶有HIV病毒的東西，但有三次意外事故正好成為證明。美國實驗室的工作人員偶然間暴露在了HIV測試呈陽性的環(huán)境中，而此后，三次事故中的工作人員都患上了艾滋病。

    誤解二：抗病毒藥物是"毒藥"

    解析：抗病毒治療的確會產生多種副作用。副作用輕者只是感覺惡心或者做奇怪的夢，重者如一些神經(jīng)損傷如果不得到及時救治甚至會危及生命。一些副作用表現(xiàn)持續(xù)時間很短，而有些則會持續(xù)很長時間。

    然而對于西方采用最新抗病毒療法的人們來說，副作用基本不算什么問題。并且不管使用新療法還是舊療法，在世界各地進行的許多測試都證明這種療法的利遠大于弊。舉個例子，一項耗時2年針對1255名病人的研究結果顯示，經(jīng)過治療，死亡率從每年29%下降到每年9%以下。

    誤解三：HIV測試有缺陷

    解析：ELISA測試和西方點測（western blot）是兩種最普遍用來檢測HIV抗體的測試，ELISA測試以前偶爾會出現(xiàn)誤報，例如如果有人近期打過流感疫苗，流感抗體引起的交叉反應會導致HIV測試結果呈陽性。然而，20世紀90年代中期這一問題已經(jīng)得到了解決。另外，ELISA測試呈陽性的患者還要再經(jīng)過更加復雜更加精確也更加昂貴的西方點測確認，才會被最終確診。結果是現(xiàn)在誤診率已經(jīng)降到了千分之一以下。

    誤解四：貧窮或營養(yǎng)不良引發(fā)艾滋病

    解析：這一條經(jīng)常被用來解釋為何非洲艾滋病發(fā)病率較高。在烏干達Rakai區(qū)進行的一項研究中，研究人員跟蹤調查2萬名成人達三年之久。因艾滋病死亡比例最高的是受過良好教育的人或政府雇員，換句話說，中產階級比窮人因艾滋病導致的死亡率更高。

    即使在反對聲音最集中的南非，幾年時間里數(shù)據(jù)都成為反駁貧窮說的最好證據(jù)。南非的一項死亡統(tǒng)計研究發(fā)現(xiàn)2002年的死亡率比1997年高出57%,而該國在相應時間中的貧窮和營養(yǎng)不良比例并未上升，根據(jù)當?shù)卣�府的說法，貧窮人口數(shù)量實際上還下降了。

    誤解五：在西方HIV并未大規(guī)模傳播證明認為HIV是通過性傳播的傳統(tǒng)說法是錯的

    解析：二十世紀80年代早期，到處充斥著HIV會從高危的同性戀和吸毒人群傳向大量普通民眾的預言。在撒哈拉以南的非洲，HIV確實在異性戀人群中快速蔓延，例如在南非成人患病率高達18%.而在西方以及非洲以外的許多發(fā)展中國家，HIV很大程度上仍只在特定小眾人群中傳播。

    為什么HIV病毒在有些人群中傳播得很快而在其他人群中則慢得多，圍繞這一點一直有很多爭議。有一種理論是認為非洲流行的HIV更易通過陰道性交傳播，而非洲以外地區(qū)的HIV則更容易通過肛交傳播。

    另一種解釋是"同期理論".在非洲一些國家，HIV在異性戀中傳播很廣，主要是由于那里的人們一般同時有兩個或者更多長期性伴侶，加速了HIV的擴散。相反，西方的異性戀或許終其一生會有幾個性伴侶，但一般在一段時間內相對比較專一。如果某人感染了HIV病毒，起碼在幾個月或者幾年的時間里，他不會通過性交向更多人傳播。