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Which animal SARS-COV-2 leapt from to infect human beings remains unknown.
目前還不清楚究竟是哪種動物將SARS-COV-2傳染給了人類。
But the evidence suggests that bats were involved at some point—perhaps not as the immediate source of the virus,
但有證據表明，蝙蝠在某種程度上參與了病毒的傳播——也許不是作為病毒的直接來源，
but probably as the reservoir from which it ultimately came.
而是作為病毒的最終來源。
Almost certainly that was true of the virus which caused the original SARS outbreak, in 2002.
幾乎可以肯定的是，導致2002年SARS爆發的病毒就是如此。
Though this was transmitted to people by palm civets, they probably caught it from horseshoe bats.
雖然這種病毒是通過椰子貓傳染給人類的，但椰子貓可能是被菊頭蝠感染的。
MERS, another coronavirus, is similarly suspected of starting in bats, though the immediate source of human infection is camels.
另一種冠狀病毒，中東呼吸綜合征冠狀病毒也被懷疑是由蝙蝠引起的，盡管導致人類感染的直接來源是駱駝。
Bats are also reckoned to be behind the spread of Ebola and Marburg fevers,which are viral infections as well, though not caused by coronaviruses.
蝙蝠也被認為是埃博拉病毒和馬爾堡熱傳播的幕后推手，盡管這兩種就并不是由冠狀病毒引起的，但它們也是病毒感染。
And vampire bats famously carry another virus, rabies.
吸血蝠還攜帶著另一種著名的病毒——狂犬病。
The idea that this may not be a coincidence has led people to ask if there is something special about bats
人們認為這可能不是巧合，這一想法這讓人們不禁要問，蝙蝠是否有什么特別之處
which encourages the evolution within them of viruses predisposed to jump the species barrier and infect other sorts of animals. At the moment, the evidence is mixed.
促使病毒在它們體內進化，從而有可能跨越物種屏障，感染其他種類的動物。目前，證據比較混亂。
In favour of the idea is an experiment conducted recently by Cara Brook of the University of California, Berkeley, and published in February in eLIFE.
支撐這一想法的是近期由加州大學伯克利分校的Cara Brook進行并于2月發表于《eLIFE》的一項實驗。
This suggests a possible mechanism. Some bats have unusual immune systems,
這暗示了一種可能的機制。一些蝙蝠擁有不同尋常的免疫系統，
in which an antiviral process known as the interferon pathway is always active, rather than being switched on in response to infection.
在該系統中，被稱為干擾素通路的抗病毒過程始終保持活躍，而不是僅在感染時被激活。
Dr Brook and her colleagues conducted experiments on cells from bats that have this arrangement and on others which do not
Brook博士和她的同事對擁有該種免疫系統以及沒有這種系統的蝙蝠的細胞進行實驗，
(and also on cells from monkeys, as a control). They concluded that always-on interferon pathways probably do speed up viral evolution.
（作為對照，也對猴子的細胞進行了實驗）。他們總結稱，永遠活躍的干擾素通路可能確實加快了病毒進化。
That would make bats more abundant sources of virulent new viruses than other groups of mammals.
這會讓蝙蝠成為比其他哺乳動物更豐富的新病毒來源。
Against the idea, however, is work published this week in the Proceedings of the National Academy of Sciences
然而，反對這種觀點的是本周由格拉斯哥大學的Nardus Mollentze和Daniel Streicker
by Nardus Mollentze and Daniel Streicker of the University of Glasgow.
發表于《Proceedings of the National Academy of Sciences》的一項研究。
Dr Mollentze and Dr Streicker found that the number of viruses which have passed to people from 11 orders of mammals and birds
Mollentze和Streicker博士發現，11目哺乳動物和鳥類傳給人類的病毒數量
is pretty much proportional to the number of species in each order. Bats are the second-most diverse mammalian order, after rodents.
與每一目中物種的數量成比例。蝙蝠是僅次于嚙齒動物的第二大哺乳動物目。
"It is therefore not surprising", Dr Mollentze observes, "that as a group they are associated with a large number of viruses."
Mollentze博士表示：“因此，作為一個群體，它們與大量的病毒有關，這并不奇怪。”
Although bat immune systems do indeed have the unusual features that interested Dr Brook and her colleagues,
雖然，蝙蝠的免疫系統確實有讓Brook博士和她的同事感興趣的特點，
Dr Mollentze and Dr Streicker found no evidence these caused bat-associated viruses to be more numerous
但Mollentze博士和Streicker博士并沒有發現證據證明，這導致與蝙蝠相關的病毒
or more prone to infect people than viruses associated with other animal groups.
比與其他動物群體相關的病毒數量更多或更容易感染人類。
This study is in line with work done specifically on coronaviruses by Tracey Goldstein of University of California, Davis.
該研究與加州大學戴維斯分校的Tracey Goldstein針對冠狀病毒的專門研究相一致。
In 2017 she and her colleagues published a piece of research in which they had tested for coronaviruses in bats,
2017年，她和她的同事發表了一項研究，她們在非洲、南非和亞洲的20個國家
rodents and primates (including people) in 20 countries in Africa, South America and Asia.
對蝙蝠、嚙齒動物和靈長類動物（包括人類）的冠狀病毒進行了測試。
Individual bat species normally had between one and five types of coronavirus.
單個蝙蝠種類通常攜帶冠狀病毒類型的數量在1到5種之間。
(For comparison, human beings have seven, including the newly emerged SARS-COV-2.)
（作為比較，人類是7種，包括新出現的SARS-COV-2。）
Scale that up for the 1,400 different species of the animals and it means there are potentially more than 3,000 coronaviruses circulating in bats.
如果擴大到1400種不同種類的動物，那么這就意味著可能有超過3000種冠狀病毒在蝙蝠體內流通。
This certainly increases the odds that bats will be responsible for generating a coronavirus dangerous to people. But only because there are lots of them.
這無疑增加了蝙蝠產生對人類危險的冠狀病毒的可能性。但這也只是因為它們數量眾多。
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