主题：【讨论】The Truth of Covid-19 -- EasonChan

NEW YORK (AP) — A new analysis of blood samples from 24,000 Americans taken early last year is the latest and largest study to suggest that the new coronavirus popped up in the U.S. in December 2019 — weeks before cases were first recognized by health officials.

The analysis is not definitive, and some experts remain skeptical, but federal health officials are increasingly accepting a timeline in which small numbers of COVID-19 infections may have occurred in the U.S. before the world ever became aware of a dangerous new virus erupting in China.

“The studies are pretty consistent,” said Natalie Thornburg of the Centers for Disease Control and Prevention.

“There was probably very rare and sporadic cases here earlier than we were aware of. But it was not widespread and didn’t become widespread until late February,” said Thornburg, principal investigator of the CDC’s respiratory virus immunology team.

Such results underscore the need for countries to work together and identify newly emerging viruses as quickly and collaboratively as possible, she added.

The pandemic coronavirus emerged in Wuhan, China in late 2019. Officially, the first U.S. infection to be identified was a traveler — a Washington state man who returned from Wuhan on Jan. 15 and sought help at a clinic on Jan. 19.

CDC officials initially said the spark that started the U.S. outbreak arrived during a three-week window from mid-January to early February. But research since then — including some done by the CDC — has suggested a small number of infections occurred earlier.

A CDC-led study published in December 2020 that analyzed 7,000 samples from American Red Cross blood donations suggested the virus infected some Americans as early as the middle of December 2019.

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The latest study, published Tuesday online by the journal Clinical Infectious Diseases, is by a team including researchers at the National Institutes of Health. They analyzed blood samples from more than 24,000 people across the country, collected in the first three months of 2020 as part of a long-term study called “All Of Us” that seeks to track 1 million Americans over years to study health.

Like the CDC study, these researchers looked for antibodies in the blood that are taken as evidence of coronavirus infection, and can be detected as early as two weeks after a person is first infected.

The researchers say seven study participants — three from Illinois, and one each from Massachusetts, Mississippi, Pennsylvania, and Wisconsin — were infected earlier than any COVID-19 case was originally reported in those states.

One of the Illinois cases was infected as early as Christmas Eve, said Keri Althoff, an associate professor at the Johns Hopkins Bloomberg School of Public Health and the study’s lead author.

It can be difficult to distinguish antibodies that neutralize SARS-CoV-2, the virus that causes COVID-19, from antibodies that fight other coronaviruses, including some that cause the common cold. Researchers in both the NIH and CDC studies used multiple types of tests to minimize false positive results, but some experts say it still is possible their 2019 positives were infections by other coronaviruses and not the pandemic strain.

“While it is entirely plausible that the virus was introduced into the United States much earlier than is usually appreciated, it does not mean that this is necessarily strong enough evidence to change how we’re thinking about this,” said William Hanage, a Harvard University expert on disease dynamics.

The NIH researchers have not followed up with study participants yet to see if any had traveled out of the U.S. prior to their infection. But they found it noteworthy that the seven did not live in or near New York City or Seattle, where the first wave of U.S. cases were concentrated.

“The question is how did, and where did, the virus take seed,” Althoff said. The new study indicates “it probably seeded in multiple places in our country,” she added.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.

纽约（美联社）--对去年年初取自2.4万名美国人的血样进行的一项新的分析是最新和最大的研究，表明新的冠状病毒于2019年12月在美国突然出现--在病例首次被卫生官员确认之前数周。

该分析不是确定的，一些专家仍然持怀疑态度，但联邦卫生官员越来越接受一个时间表，即在世界意识到中国爆发危险的新病毒之前，美国可能已经出现了少量的COVID-19感染。

"疾病控制和预防中心的Natalie Thornburg说："这些研究是相当一致的。

"这里可能有非常罕见的零星病例，比我们所知道的要早。但是它并不普遍，直到2月下旬才变得普遍，"CDC呼吸道病毒免疫学小组的首席调查员索恩伯格说。

她补充说，这样的结果强调了各国需要共同努力，并尽可能迅速和协作地识别新出现的病毒。

大流行性冠状病毒于2019年底在中国武汉出现。官方称，第一个被确认的美国感染者是一名旅行者--一名华盛顿州男子，他于1月15日从武汉返回，并于1月19日在一家诊所寻求帮助。

疾病预防控制中心的官员最初说，引发美国疫情的火花是在1月中旬至2月初的三周时间内出现的。但是此后的研究--包括CDC所做的一些研究--表明少量的感染发生在更早的时候。

2020年12月发表的一项由CDC领导的研究分析了来自美国红十字会献血的7000个样本，表明该病毒早在2019年12月中旬就感染了一些美国人。

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最新的研究报告周二在《临床传染病》杂志上在线发表，是由包括美国国立卫生研究院的研究人员在内的一个团队完成的。他们分析了全国各地24000多人的血样，这些血样是在2020年前三个月收集的，是一项名为 "All Of Us "的长期研究的一部分，该研究旨在多年来追踪100万美国人，以研究健康状况。

与CDC的研究一样，这些研究人员寻找血液中的抗体，这些抗体被当作冠状病毒感染的证据，并且可以在一个人第一次被感染后的两周内检测出来。

研究人员说，七个研究参与者--三个来自伊利诺伊州，一个来自马萨诸塞州、密西西比州、宾夕法尼亚州和威斯康星州--被感染的时间早于这些州最初报告的任何COVID-19病例。

约翰霍普金斯大学彭博公共卫生学院副教授、该研究的主要作者Keri Althoff说，其中一个伊利诺伊州的病例早在圣诞节前夕就被感染了。

要区分中和SARS-CoV-2（导致COVID-19的病毒）的抗体和对抗其他冠状病毒（包括一些导致普通感冒的病毒）的抗体可能很困难。美国国立卫生研究院和疾病预防控制中心的研究人员使用了多种类型的测试，以尽量减少假阳性结果，但一些专家说，他们的2019年阳性结果仍有可能是其他冠状病毒的感染，而不是大流行的病毒株。

"哈佛大学疾病动力学专家William Hanage说："虽然该病毒被引入美国的时间比人们通常认为的要早得多，但这并不意味着这一定是强有力的证据，足以改变我们对此事的思考方式。

美国国立卫生研究院的研究人员还没有对研究参与者进行跟踪调查，以了解是否有人在感染前曾离开过美国。但他们发现值得注意的是，这七人没有住在纽约市或西雅图附近，而美国的第一波病例都集中在那里。

"Althoff说："问题是病毒是如何以及在哪里播种的。新的研究表明 "它可能在我们国家的多个地方播种，"她补充说。

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美联社健康和科学部得到霍华德-休斯医学研究所科学教育部的支持。美联社对所有内容全权负责。