Public-health officials in the U.S. are striving to keep tabs on thousands of Americans who have quarantined themselves at home after returning from mainland China to curtail the new coronavirus, adding to an epidemic response that is straining already-stretched local departments.

More than 5,400 people had been asked to self-quarantine in California alone as of Feb. 14, according to the California Department of Public Health. Hundreds more are self-quarantining in Georgia, Washington state, Illinois, New York and other states.

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