COVID-19 : Variations on a theme
新冠肺炎出现变种
Natural selection is a powerful force. In circumstances that are still disputed, it took a bat coronavirus and adapted it to people instead.
自然选择很强大，在一些有争议的情况下，蝙蝠冠状病毒可能会寄宿在人身上。
The result has spread around the globe. Now, in two independent but coincidental events, it has modified that virus still further, creating new variants which are displacing the original versions.
新冠病毒已经袭击全球。现在，在两个独立但又巧合的案例中，人们却发现病毒仍在进化，产生新变种代替原来的毒株。
It looks possible that one or other of these novel viruses will itself soon become a dominant form of SARS-CoV-2.
其中有些变种不久后就可能成为新冠病毒的主要毒株。
Knowledge of both became widespread in mid-December.
在十二月中，上述两个事件已经人尽皆知。
In Britain , a set of researchers called the COVID-19 Genomics UK Consortium (COG-UK) published the genetic sequence of variant B.1.1.7, and NERVTAG, a group that studies emerging viral threats, advised the government that this version of the virus was 67-75% more transmissible than those already circulating in the country.
来自新冠肺炎英国基因组学联盟的研究员公布了B.1.1.7变种的基因序列，新型呼吸道病毒威胁咨询小组向政府建议，认为该变种的传染性是已传播病毒的1.67至1.75倍。
In South Africa, meanwhile, Salim Abdool Kalim, a leading epidemiologist, briefed the country on all three television channels about a variant called 501.V2 which, by then, was accounting for almost 90% of new COVID-19 infections in the province of Western Cape.
与此同时，来自南非的流行病学带头人专家Salim Abdool Kalim在三个电视频道上向全国解读501.V2变种，该变种当时已经导致西开普省90%新出现的新冠感染。
Britain responded on December 19th, by tightening restrictions already in place.
英国在12月19日作出响应，加强了已有的限制。
South Africa’s response came on December 28th, in the wake of its millionth recorded case of the illness, with measures that extended a night-time curfew by two hours and reimposed a ban on the sale of alcohol.
在染病人数达一百万后，南非在12月28日作出响应，采取措施将宵禁延长两小时，并再次禁止销售酒精饮料。
Other countries have reacted by discouraging even more forcefully than before any travel between themselves and Britain and South Africa.
对此，其他国家已经更为大力地阻止与本国与英国和南非之间的旅行。
At least in the case of b.1.1.7, though, this has merely shut the stable door after the horse has bolted.
然而，至少就b.1.1.7变种而言，这也于事无补了。
That variant has now been detected in a score of countries besides Britain—and from these new sites, or from Britain, it will spread still further.
该变种从除了英国之外的很多国家中也发现了，该变种也将从这些新地点，或是从英国继续传播。
Isolated cases of 501.V2 outside South Africa have been reported, too, from Australia, Britain, Japan and Switzerland.
在南非以外的501.V2毒株感染个别案例也被上报，来自于澳大利亚、英国、日本和瑞士。
So far , the evidence suggests that despite their extra transmissibility, neither new variant is more dangerous on a case-by-case basis than existing versions of the virus.
到目前为止，有证据显示，尽管新变种有极强的传染性，从病例角度来看，两者并不比已有病毒更加致命。
In this, both are travelling the path predicted by evolutionary biologists to lead to long-term success for a new pathogen—which is to become more contagious (which increases the chance of onward transmission) rather than more deadly (which reduces it).
这样来看，两个变种都沿着进化生物学家所预测的方向成功朝着新的病原体演进，变得更加有感染性（这能增加其传播的几率），而不是更加有致命性（这能降低其传播的几率）。
And the speed with which they have spread is impressive.
而且它们传播的速度也很惊人。
