In the early 2000s, a coronavirus infecting bats jumped into raccoon dogs and other wild mammals in southwestern China. Some of those animals were sold in markets, where the coronavirus jumped again, into humans. The result was the SARS pandemic, which spread to 33 countries and claimed 774 lives. A few months into it, scientists discovered the coronavirus in mammals known as palm civets sold in a market at the center of the outbreak.

本世纪初，一种感染蝙蝠的冠状病毒在中国西南部感染了貉和其他野生哺乳动物。其中一些动物在市场上出售，冠状病毒再次传染给人类。其结果是一场SARS大流行，蔓延到33个国家，夺走了774人的生命。几个月后，科学家在疫情爆发中心的一个市场上出售的一种名为果子狸的哺乳动物身上发现了冠状病毒。

In a study published on Wednesday, a team of researchers compared the evolutionary story of SARS with that of Covid 17 years later. The researchers analyzed the genomes of the two coronaviruses that caused the pandemics, along with 248 related coronaviruses in bats and other mammals.

在周三发表的一项研究中，一组研究人员将SARS的进化过程与17年后的Covid进行了比较。研究人员分析了导致疫情的两种冠状病毒的基因组，以及蝙蝠和其他哺乳动物中248种相关冠状病毒的基因组。

Jonathan Pekar, an evolutionary virologist at the University of Edinburgh and an author of the new study, said that the histories of the two coronaviruses followed parallel paths. “In my mind, they are extraordinarily similar,” he said.

爱丁堡大学的进化病毒学家、这项新研究的作者之一乔纳森·佩卡尔说，这两种冠状病毒的历史遵循平行的路径。“在我看来，它们非常相似，”他说。

In both cases, Dr. Pekar and his colleagues argue, a coronavirus jumped from bats to wild mammals in southwestern China. In a short period of time, wildlife traders took the infected animals hundreds of miles to city markets, and the virus wreaked havoc in humans.

佩卡尔和他的同事们认为，在这两个案例中，冠状病毒都是从中国西南部的蝙蝠传染给野生哺乳动物的。在很短的时间内，野生动物贩子将感染的动物带到数百公里外的城市的市场，随后病毒给人类带来一场浩劫。

“When you sell wildlife in the heart of cities, you’re going to have a pandemic every so often,” said Michael Worobey, an evolutionary biologist at the University of Arizona and an author of the new study.

“在城市中心出售野生动物，就会经常爆发流行病，”亚利桑那大学的进化生物学家、这项新研究的作者之一迈克尔·沃罗贝说。

The study lands at a fraught political moment. Last month the White House created a web page called “Lab Leak: The True Origin of Covid 19,” asserting that the pandemic had been caused not by a market spillover but by an accident in a lab in Wuhan, China.

这项研究出现在一个令人担忧的政治时刻。上个月，白宫创建了一个名为“实验室泄漏：Covid-19的真正起源”的网页，声称大流行的起因不是市场溢出，而是中国武汉一家实验室的意外事故。

On Friday, in its proposed budget, the White House described the lab leak as “confirmed” and justified an $18 billion cut to the National Institutes of Health in part on what it described as the agency’s “inability to prove that its grants to the Wuhan Institute of Virology were not complicit in such a possible leak.”

周五，白宫在其预算提案中称，实验室泄密事件“已得到证实”，并为削减美国国立卫生研究院的180亿美元拨款提供了理由，部分原因是该机构“无法证明其向武汉病毒研究所提供的拨款与这样一起可能的泄漏事件无关”。

The Chinese government responded with a flat denial that Covid had been caused by a Wuhan lab leak and raised the possibility that the virus had come instead from a biodefense lab in the United States.

中国政府断然否认新冠病毒是由武汉的实验室泄漏造成的，并提出了病毒来自美国国防生物实验室的可能性。

“A thorough and in-depth investigation into the origins of the virus should be conducted in the U.S.,” the statement read.

其声明称：“应该对美国开展全面深入的新冠病毒溯源调查。”

Sergei Pond, a virologist at Temple University, said that he did not consider the origin of Covid settled. But he worried that the incendiary language from the two governments would make it difficult for scientists to investigate — and debate — the origin of Covid.

天普大学的病毒学家谢尔盖·庞德表示，他不认为新冠病毒的起源已经确定。但他担心，两国政府的煽动性言论将使科学家难以调查和辩论新冠病毒的起源。

“If it wasn’t tragic, you’d have to laugh, it’s so farcical,” Dr. Pond said.

庞德说：“如果这不是一场悲剧，你肯定都要笑出来了，因为实在太滑稽了。”

武汉病毒研究所。美国科学家的确指责过该研究所在冠状病毒实验中防护不严，但没有人提供证据表明，SARS-CoV-2的祖先在大流行之前就在该实验室。

In the first weeks of the Covid pandemic in early 2020, claims circulated that the virus responsible, SARS-CoV-2, was a biological weapon created by the Chinese Army. A group of scientists who analyzed the data available at the time rejected that idea. Although they couldn’t rule out an accidental lab leak, they favored a natural origin of Covid.

2020年初新冠疫情的最初几周曾流传一个说法，称导致疫情的病毒SARS-CoV-2是中国军队制造的一种生物武器。一组科学家在分析了当时可用的数据后否定了这一观点。尽管他们不能排除实验室意外泄漏的可能性，但他们倾向于认为新冠病毒是自然起源的。

As Dr. Worobey and other scientists started studying the origin of Covid, American intelligence agencies were also assessing it. Their assessments have been mixed. The F.B.I., and the C.I.A. favor an escape from the Wuhan Institute of Virology, although with only low certainty. The Department of Energy leans with low confidence to the virus escaping from a different lab in Wuhan. Other agencies lean toward a natural origin.

当沃罗贝和其他科学家开始研究新冠病毒的起源时，美国情报机构也在对其进行评估。他们的评估结果不一。联邦调查局和中央情报局倾向于认为从武汉病毒研究所逃逸，不过确定性不高。美国能源部认为病毒是从武汉的另一个实验室逃逸的，但置信度为低。其他机构倾向于自然来源。

The agencies have not made their evidence or their analyses public, and so scientists cannot evaluate the basis of their conclusions. However, Dr. Worobey and other researchers have published a string of papers in scientific journals. Along the way, Dr. Worobey became convinced that the Covid pandemic had started at the Huanan Seafood Market in Wuhan.

这些机构没有公开它们的证据或分析，因此科学家无法评估它们结论的基础。然而，沃罗贝和其他研究人员在科学期刊上发表了一系列论文。在研究过程中，沃罗贝确信，新冠疫情是从武汉的华南海鲜市场开始的。

“Scientifically, it’s as clear as H.I.V. or Spanish flu,” Dr. Worobey said, referring to two diseases whose origins he has also studied.

“从科学角度来说，这和HIV病毒或西班牙流感一样清楚，”沃罗贝说。他也研究过这两种疾病的起源。

For the new study, Dr. Worobey, Dr. Pekar and their colleagues compared the genomes of 250 coronaviruses, using their genetic similarities and differences to determine their relationships. They were able to reconstruct the history of the coronaviruses that cause both SARS and Covid — known as SARS-CoV and SARS-CoV-2.

在这项新研究中，沃罗贝、佩卡尔及其同事比较了250种冠状病毒的基因组，利用它们的遗传相似性和差异来确定它们之间的关系。他们能够重建导致SARS和Covid的冠状病毒的历史，即SARS-CoV病毒和SARS-CoV-2病毒。

The ancestors of both coronaviruses circulated in bats across much of China and neighboring countries for hundreds of thousands of years. In the last 50 years or so, their direct ancestors infected bats that lived in southwestern China and northern Laos.

这两种冠状病毒的祖先在中国大部分地区和邻国的蝙蝠中传播了数十万年。在过去50年左右的时间里，它们的直系祖先感染了生活在中国西南部和老挝北部的蝙蝠。

As the coronaviruses infected the bats, they sometimes ended up inside a cell with another coronavirus. When the cell made new viruses, it accidentally created hybrids that carried genetic material from both of the original coronaviruses — a process known as recombination.

当冠状病毒感染蝙蝠后，有时会与另一种冠状病毒一起进入细胞。当细胞制造新病毒时，它意外地产生了携带两种原始冠状病毒遗传物质的杂交体，这一过程被称为重组。

“These aren’t ancient events,” said David Rasmussen, a virologist at North Carolina State University who was not involved in the new study. “These things are happening all the time. These viruses are truly mosaics.”

没有参与这项新研究的北卡罗来纳州立大学病毒学家戴维·拉斯穆森说：“这些都不是古老的事件。这种事一直在发生。这些病毒真的可以说是东拼西凑。”

In 2001, just a year before the SARS pandemic started in the city of Guangzhou, the researchers found, SARS-CoV underwent its last genetic mixing in bats. Only after that last recombination could the virus have evolved into a human pathogen. And since Guangzhou is several hundred miles from the ancestral region of SARS-CoV, bats would not have been able to bring the virus to the city in so little time.

研究人员发现，2001年，也就是SARS在广州造成大流行的前一年，SARS-CoV病毒在蝙蝠中进行了最后一次基因混合。只有经过最后一次重组之后，病毒才进化成人类病原体。由于广州距离SARS-CoV病毒的发源地有几百公里，蝙蝠不可能在这么短的时间内将病毒带到广州。

Instead, researchers generally agree, the ancestors of SARS-CoV infected wild mammals that were later sold in markets around Guangzhou. A few months after the start of the SARS pandemic, researchers discovered SARS-CoV in palm civets and other wild mammals for sale in markets.

研究人员普遍认为是SARS-CoV的祖先感染了野生哺乳动物，而后这些哺乳动物在广州周边的市场上出售。SARS疫情开始几个月后，研究人员在市场上出售的果子狸和其他野生哺乳动物身上发现了SARS-CoV。

The researchers found a similar pattern when they turned to SARS-CoV-2, the cause of Covid. The last recombination in bats took place between 2012 and 2014, just five to seven years before the Covid pandemic, several hundred miles to the northeast, in Wuhan.

当研究人员研究导致新冠疫情的SARS-CoV-2时，他们发现了类似的模式。蝙蝠身上的最后一次重组发生在2012年至2014年之间，也就是新冠大流行前五到七年，地点在东北方向几百公里外的武汉。

That was also a substantial departure from the region where the virus’s ancestors had circulated. But it was comparable to the journey that SARS-CoV took, courtesy of the wildlife trade.

这也大大偏离了该病毒祖先的流行区域。但传播过程与SARS-CoV相似，都是通过野生动物贸易。

Proponents of lab-leak theories have highlighted the long distance between Wuhan and the locations where the closest relatives of SARS-CoV-2 have been found. If bats could not fly to the region around Wuhan and infect wild mammals there, they maintain, then scientists must have collected the coronavirus from bats in southwest China and tinkered with it in their lab, from which it then escaped.

实验室泄漏理论的支持者强调了武汉与发现SARS-CoV-2近亲的地点之间的距离。他们坚持认为，如果蝙蝠不能飞到武汉周边地区并感染那里的野生哺乳动物，那么科学家一定是从中国西南地区的蝙蝠身上收集了冠状病毒，并在实验室里对其进行了处理，然后病毒从那里逃逸出来。

American scientists have criticized the Wuhan Institute of Virology for lax safeguards in their coronavirus experiments. But no one has offered evidence that the progenitor of SARS-CoV-2 was at the Wuhan Institute of Virology before the pandemic. The new study by Dr. Worobey and his colleagues shows that bat coronaviruses can travel long distances without the help of scientists, through the wildlife trade.

美国科学家批评武汉病毒研究所在冠状病毒实验中防护不严。但没有人提供证据证明SARS-CoV-2的前身在大流行之前就在武汉病毒研究所。沃罗贝及其同事的新研究表明，蝙蝠冠状病毒可以通过野生动物贸易，在没有科学家帮助的情况下长距离传播。

The researchers argue that these findings agree with studies that they published in 2022, which pointed to the Huanan Seafood Market in Wuhan as the place where the Covid pandemic got its start. Wild mammals were sold there; many early cases of Covid were recorded there, and Chinese researchers collected different strains of SARS-CoV-2 carrying distinct mutations there. Dr. Worobey and his colleagues argued that the virus had twice spilled over from wild mammals at the market.

研究人员认为，这些发现与他们在2022年发表的研究一致，该研究指出武汉的华南海鲜市场是新冠疫情的发源地。野生哺乳动物在那里出售；那里记录了许多早期病例，中国研究人员在那里收集了携带不同突变的不同SARS-CoV-2毒株。沃罗贝和他的同事们认为，这种病毒曾两次从市场上的野生哺乳动物身上传播出去。

Marc Eloit, the former director of the Pathogen Discovery Laboratory at Pasteur Institute in Paris, said that the new study was significant for providing a clear picture of where SARS-CoV-2 came from.

巴黎巴斯德研究所病原体发现实验室前主任马克·埃洛伊特说，这项新研究对确切了解SARS-CoV-2的来源具有重要意义。

But he also observed that the coronavirus was markedly different from its closest known relatives in bats. After it split from those viruses, it must have mutated or undergone recombination to become well adapted for spreading in humans.

但他也观察到，这种冠状病毒与蝙蝠中的已知近亲有明显不同。从这些病毒中分离出来后，它必须发生突变或经历重组，才能很好地适应在人类中传播。

“I maintain that the possibility of a recombination event — whether accidental or deliberate — in a laboratory setting remains just as plausible as the hypothesis of emergence via an intermediate host on the market,” Dr. Eloit said.

埃洛伊特说：“我坚持认为，在实验室环境中发生重组事件的可能性——无论是偶然的还是故意的——与通过市场上的中间宿主出现的假设一样可信。”

Dr. Eloit and other scientists agreed that finding an intermediate form of SARS-CoV-2 in a wild mammal would make a compelling case for a natural spillover. Chinese authorities looked at some animals at the start of the pandemic and did not find the virus in them.

埃洛伊特和其他科学家一致认为，在野生哺乳动物中发现中间形式的SARS-CoV-2将为自然溢出提供令人信服的解释。中国政府在大流行开始时对一些动物进行了检查，但没有在它们身上发现这种病毒。

However, wildlife vendors at the Huanan market removed their animals from the stalls before scientists could study them. And once China put a stop to wildlife sales, farmers culled their animals.

然而，华南市场上的野生动物商贩在科学家们研究它们之前，就把他们的动物从摊位上搬走了。中国禁止野生动物交易后，农民们纷纷宰杀了手头的动物。

“There’s a big missing piece, and you really can’t dance around it,” said Dr. Pond.

“缺了很大一块，这是个很难绕过去的问题，”庞德说。