经济学人下载:直到死神将我们分开

Science and technology
科学技术

HIV and AIDS
人体免疫缺陷病毒和获得性免疫缺陷综合征

Till death do us part
直到死神将我们分开

Putting numbers on infidelity
细数出轨之罪

ONE of the problems of dealing with a sexually transmitted disease, such as AIDS, is that people routinely lie about their indulgence in the sorts of behaviours which pass it on.
谈到性病，比如艾滋病，难题之一便是人们通常会隐瞒自己的纵欲史，而这恰恰是导致染病的原因。

That makes knowing where to put your effort harder than it need be.
我们此刻恍然大悟，夫妻之间想要保证忠诚应该花更大力气。

And in no area do people lie more than on the question of infidelity.
而且，在对婚姻不忠这个问题上，人们撒的谎比其它地方撒的谎都多。

The naive outsider might be forgiven for thinking that infidelity was likely to be an important way that HIV, the virus which causes AIDS, is spread. Until now, however, that was mere supposition.
如果围城之外的人们天真的认为艾滋病毒扩散的主要传播途径可能与婚外偷腥有关，那么我们可以原谅他们。当然，现在看来那也仅仅是猜测罢了。

Steven Bellan of the University of Texas at Austin has changed this, with a paper in the Lancet.
德州大学奥斯丁分校的史蒂夫·贝兰博士发表在《柳叶刀》上一篇论文，研究成果代替了猜测。

Using data likely to be more reliable than answers to the question:
数据示人可能会比结论对问题的方式更容易取信于人：

have you been cheating on your wife/husband?
你对自己的妻子或丈夫撒过谎吗？

he and his colleagues have worked out how much HIV infection is caused by adultery.
他与同事的研究成果显示了究竟多少例艾滋感染是由婚外偷腥造成的。

The answer, as might be expected, is a lot.
答案猜也能猜得到：非常多。

Dr Bellan and his colleagues reached this conclusion from a survey of 27,000 married or cohabiting couples in 18 African countries.
面对来自非洲18个国家2.7万接受调查的配偶，

The survey looked at who in these couples was infected, how long the couple had lived together, and the age at which each member of each couple first became sexually active.
或者是同居男女，贝兰博士和同事们将调查范围缩小在三个问题上：两个人中谁是感染者、同居或者已婚多久以及每一对之中首先成为性欲亢进的一方的年龄。

Most people do not routinely lie about these things, except for age of first sexual encounter.
如果不是第一次性行为，一般情况下大多数人不会对这三个问题有所隐瞒。

The researchers took account of that by showing that claims as much as a year at variance with the truth would make little difference to the outcome.
研究者们考虑到了这一点，指出对事实的陈述的差异如果在一年之内对结果无太大影响。

Dr Bellan plugged the results into a mathematical model that also takes account of HIV's prevalence in a country and how long people there live once they have been infected.
依据艾滋病在一个国家的传播程度和染病后人们的寿命时长，贝兰博士利用数学模型将其展现出来。

This let him estimate what proportion of HIV infections had come about by one or other member of a couple having been unfaithful, as opposed to having been infected before the couple got together, or having caught the virus from a partner so infected.
这样他就可以在相较于二人结婚之前一方染病或者结婚之后携带病毒的一方传染另一方的情况下，估算出由于无论是由于男方还是女方对婚姻不忠而导致感染艾滋病的比例。

The answer was between 27% and 61% for men and between 21% and 51% for women.
男性出轨染病几率为27%-61%，女性则相对较低21%-51%。

What can be done about that is a different question.
面对这样的结果，我们能做些什么？

Early in the AIDS epidemic, the virus was spread by what might be termed long-distance infidelity.
这又是一个难题。艾滋病流行早期，病毒传播途径被称为长距离婚姻不忠行为：

Lorry drivers and migrant miners, lonely and far from home, were the vectors.
离乡寂寞的货车司机和矿井农民是携带病毒的主要人群。

Those groups, however, could be made the target of campaigns designed to ask them to think about what they were up to, and to be more careful about it.
针对这些人群，我们应当策划出一些活动项目来提醒他们：你们这样做意义何在？即使寂寞难忍，也要注意防护措施。

What Dr Bellan has uncovered looks more quotidian—and thus much harder to deal with.
贝兰博士研究没有涉及的地方更为人司空见惯，因此处理起来也就更加棘手。