The U.S. government was slow to understand how much coronavirus was spreading from Europe, which helped drive the acceleration of outbreaks across the nation, a top health official said Friday.

Limited testing and delayed travel alerts for areas outside China contributed to the jump in U.S. cases starting in late February, said Dr. Anne Schuchat, the No. 2 official at the U.S. Centers for Disease Control and Prevention.

“We clearly didn’t recognize the full importations that were happening,” Schuchat told The Associated Press.

The coronavirus was first reported late last year in China, the initial epicenter of the global pandemic. But the U.S. has since become the hardest-hit nation, with about a third of the world’s reported cases and more than a quarter of the deaths.

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The CDC on Friday published an article, authored by Schuchat, that looked back on the U.S. response, recapping some of the major decisions and events of the last few months.

It suggests the nation’s top public health agency missed opportunities to slow the spread. Some public health experts saw it as important assessment by one of the nation’s most respected public health doctors.

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