[实事评说] Coronavirus was present in US earlier than initially thought: Study

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LOS ANGELES - Though the first case of the coronavirus wasn’t identified in the U.S. until January, a new study suggests that the novel disease was present earlier in the country than first thought.
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A study published Monday in the journal Clinical Infectious Diseases conducted by researchers with the Centers for Disease Control and Prevention suggests that the novel virus was present in the United States as early as mid-December 2019.