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.

    尽管有着非常有说服力的证据表明HIV是引发AIDS的原因，一个中坚科研小组仍然否定了它。（见否认AIDS:致命的误解 ）.我们发现了关于AIDS的五个最常见的不解之谜。

    不解之谜：AIDS不是由HIV病毒引起的

    解密：当然这是最大的误解。早在1983年，研究人员们就首次从艾滋病患者身上分离出HIV病毒。到1985年，研究者们已经证实绝大多数艾滋病患者的血液中存在HIV抗体。他们还指出，那些HIV病毒测试呈阳性的患者，即使最初看起来很健康，但如果不及时进行救治，不久就会患上艾滋病。

    反对者们的理由是HIV并不满足"科赫基本原理"--19世纪德国科学家罗伯特·科赫提出的这项原理列举了一系列要证明某种疾病是由某种病原体引发所需的必要条件。那个世纪病毒还未被发现，用判断细菌感染的一系列标准来判断艾滋病是否合适本身就是件值得争议的事。况且，如果不是以一种严格到可笑程度的标准衡量，HIV还大体满足科赫基本原理。

    原理1:必须在每位患病者身上都发现此种病菌。1993年，位于乔治亚州亚特兰大的美国疾病预防控制中心回顾了230179例疑似艾滋病病例。只有47人HIV病毒测试呈阴性，这一比例低于0.025%.

    原理2:病菌必需从患病者身上获得并在无菌环境下培养。HIV病毒的获取是依照现代滤过性微生物学最严格的标准执行。然而一小组名为帕斯小组（Perth Group）的澳大利亚科学家声称没有证据表明HIV病毒存在。而且，依照他们奇异的标准，引起流感，天花，黄热病，麻疹还有许多其他疾病的病毒也都不存在。

    原理3:如果将该病菌注入健康人体内，会引发健康人患上相应疾病。很显然没人愿意故意注射带有HIV病毒的东西，但有三次意外事故正好成为证明。美国实验室的工作人员偶然间暴露在了HIV测试呈阳性的环境中，而此后，三次事故中的工作人员都患上了艾滋病。

    误解二：抗病毒药物是"毒药"

    解析：抗病毒治疗的确会产生多种副作用。副作用轻者只是感觉恶心或者做奇怪的梦，重者如一些神经损伤如果不得到及时救治甚至会危及生命。一些副作用表现持续时间很短，而有些则会持续很长时间。

    然而对于西方采用最新抗病毒疗法的人们来说，副作用基本不算什么问题。并且不管使用新疗法还是旧疗法，在世界各地进行的许多测试都证明这种疗法的利远大于弊。举个例子，一项耗时2年针对1255名病人的研究结果显示，经过治疗，死亡率从每年29%下降到每年9%以下。

    误解三：HIV测试有缺陷

    解析：ELISA测试和西方点测（western blot）是两种最普遍用来检测HIV抗体的测试，ELISA测试以前偶尔会出现误报，例如如果有人近期打过流感疫苗，流感抗体引起的交叉反应会导致HIV测试结果呈阳性。然而，20世纪90年代中期这一问题已经得到了解决。另外，ELISA测试呈阳性的患者还要再经过更加复杂更加精确也更加昂贵的西方点测确认，才会被最终确诊。结果是现在误诊率已经降到了千分之一以下。

    误解四：贫穷或营养不良引发艾滋病

    解析：这一条经常被用来解释为何非洲艾滋病发病率较高。在乌干达Rakai区进行的一项研究中，研究人员跟踪调查2万名成人达三年之久。因艾滋病死亡比例最高的是受过良好教育的人或政府雇员，换句话说，中产阶级比穷人因艾滋病导致的死亡率更高。

    即使在反对声音最集中的南非，几年时间里数据都成为反驳贫穷说的最好证据。南非的一项死亡统计研究发现2002年的死亡率比1997年高出57%,而该国在相应时间中的贫穷和营养不良比例并未上升，根据当地政府的说法，贫穷人口数量实际上还下降了。

    误解五：在西方HIV并未大规模传播证明认为HIV是通过性传播的传统说法是错的

    解析：二十世纪80年代早期，到处充斥着HIV会从高危的同性恋和吸毒人群传向大量普通民众的预言。在撒哈拉以南的非洲，HIV确实在异性恋人群中快速蔓延，例如在南非成人患病率高达18%.而在西方以及非洲以外的许多发展中国家，HIV很大程度上仍只在特定小众人群中传播。

    为什么HIV病毒在有些人群中传播得很快而在其他人群中则慢得多，围绕这一点一直有很多争议。有一种理论是认为非洲流行的HIV更易通过阴道性交传播，而非洲以外地区的HIV则更容易通过肛交传播。

    另一种解释是"同期理论".在非洲一些国家，HIV在异性恋中传播很广，主要是由于那里的人们一般同时有两个或者更多长期性伴侣，加速了HIV的扩散。相反，西方的异性恋或许终其一生会有几个性伴侣，但一般在一段时间内相对比较专一。如果某人感染了HIV病毒，起码在几个月或者几年的时间里，他不会通过性交向更多人传播。