US cases of the novel coronavirus topped 1 million on Tuesday, having doubled in 18 days, and making up one-third of all infections in the world, according to a tally by Johns Hopkins University.

The downtown New York City skyline looms over pedestrians wearing masks due to coronavirus concerns, on Friday, April 10, 2020, in Jersey City, N.J. (AP)

Dr. Jana Cua, left, is swabbed as she is tested for COVID-19 at the Doris Ison Health Center on March 18, 2020, in Miami. (AP)