From://www.newswise.com/factcheck/covid-19-may-have-been-present-in-the-u-s-in-december-2019-weeks-earlier-than-previously-thought/?article_id=743093&fc=home 6park.com
一项于2020年11月发表的研究分析了2019年SARS-CoV-2抗体，发现这种新型冠状病毒可能早于科学家意识到的数周出现在美国。
索赔发行者和日期： 临床传染病2020年-11-30 6park.com
美国首例新冠肺炎病例发生在2020年1月19日，当时有一人从中国回国。根据11月30日发表在杂志上的一项研究临床传染病导致新冠肺炎大流行的新型冠状病毒的出现可能早于此前的预期数周。在这项研究中，疾病控制和预防中心分析了美国红十字会在2019年12月13日至2020年1月17日期间捐献的SARS-CoV-2抗体，并在1.1%的献血中发现了这种病毒的证据。然而，应该指出的是，病毒当时在美国的存在并不意味着它正在美国的任何地方社区中传播。
正如麦迪逊·达普切维奇在“蛇类”中所报道的.
虽然研究结果表明，这种病毒在美国的出现时间可能比以前认为的要早得多，但我们不可能知道这种病毒是通过社区传播的，还是与旅行有关的。
美国红十字会负责科学事务的副总裁苏珊·斯特莱默博士在一份新闻稿中说：“这项研究提出的可能的SARS-CoV-2感染可能是与社区或旅行有关的，这是不可能的。”他说：“一项为帮助了解旅行习惯而进行的献血者调查确定，只有不到3%的受访者报告说，在献血前28天内到美国境外旅行，而在报告捐血的人中，只有5%的人去过亚洲。”
虽然检测是专门寻找SARS-CoV-2抗体，但已知的七种其他类型的冠状病毒有一些相似之处，因此有可能发生某种程度的交叉反应。根据弗吉尼亚卫生部的说法，大多数人都会感染冠状病毒，这种病毒在他们生命中的某一时刻会导致普通感冒。而且因为血液样本对研究人员来说是匿名的，所以没有一个可以被认为是“真正的阳性”--这只能从一个接受过阳性分子诊断测试的人中确定。
此外，捐赠也可能不代表这些州的所有献血者或献血者，因此不能用于在报告日期内概括所有献血者，也不能推断研究期间国家或州的感染率水平。

COVID-19 may have been present in the U.S. in December 2019, weeks earlier than previously thought
A study published in November 2020 analyzed SARS-CoV-2 antibodies in 2019 blood bank donations and found that the novel coronavirus may have been present in the U.S. weeks earlier than scientists realized.
 6park.com
Claim Publisher and Date: Clinical Infectious Diseases on 2020-11-30 6park.com
The first case of COVID-19 in the United States was reported on January 19, 2020, when a person returned from China. According to a study published on Nov. 30 in the journal Clinical Infectious Diseases, the arrival of the novel coronavirus responsible for the COVID-19 pandemic may have been in the U.S. weeks earlier than previously thought. In the study, the Centers for Disease Control and Prevention analyzed American Red Cross blood donations for SARS-CoV-2 antibodies between Dec. 13, 2019, and Jan. 17, 2020, and found evidence of the virus in 1.1% of blood donations. It should be noted, however, that the presence of the virus in the U.S. at the time does not mean it was spreading throughout any local community in the United States.
As reported by Madison Dapcevich in Snopes...
While the findings suggested that the virus may have been present in the U.S. much earlier than previously believed, it is not possible to know whether the infection was spread through the community or associated with travel.
“It is not possible to determine whether the potential SARS-CoV-2 infections suggested by this study may have been community or travel-associated,” said Dr. Susan Stramer, vice president of Scientific Affairs at the American Red Cross, in a news release. “A previous survey of blood donors, conducted to help understand travel practices, determined that less than 3% of respondents reported travel outside of the U.S. within the 28 days prior to donation, and of those reporting travel, only 5% traveled to Asia.
Though the tests were looking for SARS-CoV-2 antibodies specifically, there are seven known types of other coronaviruses that have some similarities, so it is possible a level of cross-reactivity occurred. According to the Virginia Department of Health, most people become infected with coronaviruses that cause the common cold at some point during their lives. And because the blood samples were anonymous to researchers, none could be considered “true positives” — this can only be determined from a person who had received a positive molecular diagnostic test.
Furthermore, donations may also not represent all blood donors or donations in these states, so they cannot be used to generalize all blood donors during the dates in the report and cannot make an inference on national or state levels of infection rates during the study period.