UNITED STATES (NBC News) -- The U.S. set a new, grim record in the number of new coronavirus cases in a single day, with reports of nearly 46,000 on Friday.
The 45,942 single-day increase was driven by more than 8,000 new cases in Florida and thousands more in Texas, Arizona and California, according to an NBC News tally.
The national, one-day increase surpasses a record set Wednesday, when 45,557 new cases were reported.
A global health expert said the increase is due to much of the country's reopening when there were still many active coronavirus cases.
"This is happening because much of the country around Memorial Day, and the weeks that followed, we opened up while we still had a large number of cases," Dr. Ashish Jha, director of the Harvard Global Health Institute, told "TODAY" on Saturday, adding that the U.S. lacked the testing and contact tracing infrastructure needed to reopen safely.
"We opened up too fast. We opened up bars; we opened up nightclubs; and is the combination of all that that has led us to where we are today," Jha said.
Among all states, Arizona has seen the highest per-capita rate of coronavirus cases in the last two weeks, logging more than 400 per 100,000 residents. Arizona has 7 million residents, and its 30,000-plus new cases in that time period only falls short of the increases in California, Texas and Florida.
Coronavirus cases are up in over 20 states and territories around the country.