原文网址：https://www.cdc.gov/mmwr/volumes/69/wr/mm6928a5.htm?s_cid=mm6928a5_x
重要一段：
The sequence from March 2, 2020, (the earliest positive sentinel specimen collected) clustered with early sequences from Europe and United States (Group B), which also cluster with sequences from China. No sentinel sequences were directly connected to sequences from Wuhan, China, where the outbreak originated. This was unanticipated, given that most sentinel EDs were used by patients residing in ZIP codes with a high proportion of Chinese speakers. Rather, the sequence analysis suggests probable introductions of SARS-CoV-2 from Europe, from other U.S. locations, and local introductions from within New York. Domestic airport screening and bans on foreign nationals traveling from China were implemented on February 2;*** however, similar travel restrictions from the Schengen Area in Europe were only implemented March 13.††† Although travel restrictions are an important mitigation strategy, by the time the European restrictions were implemented, importation and community transmission of SARS-CoV-2 had already occurred in NYC.
美国疾控中心：纽约流行毒株与中国毫无关系