Across the U.S., efforts to contain the novel coronavirus escalated by the hour on Tuesday, as the number of confirmed cases topped 1,000. New York set up the country’s first “containment area” around one of the largest clusters of cases in the U.S.; colleges told students not to return campus this spring; and the Democratic presidential candidates canceled rallies in Ohio.

The U.S. had 1,001 confirmed cases of the novel coronavirus as of late Tuesday, according to data compiled by Johns Hopkins University, and state officials...