SHANGHAI—The U.S. government is working to evacuate American citizens by air from the epidemic-stricken Chinese city of Wuhan as soon as possible, according to people familiar with the effort.

The operation comes as the death toll from a newly identified coronavirus that originated in Wuhan climbs above 40 and the number of confirmed infections tops 1,300, with many of the cases in and around the central Chinese city of 11 million people.

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