NEW YORK, May 18 (Xinhua) -- The number of COVID-19 cases in the United States topped 1.5 million on Monday, reaching 1,500,753 as of 4:03 p.m. (2003 GMT), according to the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University.

Meanwhile, the national death toll of COVID-19 rose to 90,312, according to the CSSE.

New York remains the hardest-hit state with 351,371 cases and 28,339 fatalities. Other states with over 50,000 cases include New Jersey, Illinois, Massachusetts, California, Pennsylvania and Michigan, the CSSE data showed.

Over 40 states have restarted or partially restarted economy, although the country in general has not seen a downward trend in COVID-19 infection.

States and cities without the capability of being able to respond effectively and efficiently could face serious consequences if they open up prematurely, Anthony Fauci, the country's top expert on infectious diseases, told a Senate panel during a teleconference hearing on May 12.

"Even under the best of circumstances, when you pull back on mitigation, you will see some cases appear," he said. "It's the ability and the capability of responding to those cases with good identification, isolation and contact tracing will determine whether you can continue to go forward, as you try to reopen America."