The total number of coronavirus cases reported in the United States passed 4 million on Thursday, reflecting a rapid acceleration of infections detected in the country since the first case was recorded on January 21, a tally by Johns Hopkins University showed.
It took the country 98 days to reach 1 million cases, but just 16 days to go from 3 million to 4 million. The average number of new US cases is now rising by more than 2,600 every hour, the highest rate in the world.
As the pandemic has spread widely over the country, moving from the early epicentre of New York to the South and West, federal, state and local officials have clashed over how to fight it, including over how and when to ease social and economic restrictions aimed at curbing the infection rate.
Whether to order the wearing of masks, a common practice in the rest of the world and recommended by the federal government's own health experts, has become highly politicised, with some Republican governors in hard-hit states particularly resistant.
Hostility to the idea appeared to be dwindling this week, including from the Republican administration of President Donald Trump, who once dismissed mask-wearing as an effort to be politically correct.
Trump, who faces falling poll numbers over his handling of the health crisis ahead of the November election, has long refused to wear a mask in public but this week encouraged Americans to do so.
Miami Mayor Francis Suarez on Thursday said he believed his city's strict rule on mask-wearing is making a difference, citing improving numbers there.
"The remediation efforts that we've taken, including the mask in public rule, are working," he told CNN.
Another partisan point of contention is whether schools should start fully opening in August despite concerns that doing so could cause infections to spike.
Trump has threatened to withhold federal funding if schools do not reopen, but he told a press briefing on Wednesday the decision would ultimately be up to state governors.
Florida, which reported a record one-day increase in Covid-19 deaths on Thursday with 173 lives lost, has been sued by a teachers union to stop schools reopening for in-person instruction, which the union says poses an imminent threat to the health, safety and welfare of children, staff and parents.
Florida's commissioner said early in July that schools must reopen, but on Thursday Governor Ron DeSantis said parents and teachers had a choice.
"We need to provide all options," DeSantis told a news conference.
On Wednesday, Covid-19 deaths rose by more than 1,100 for a second day in a row, including record single-day increases in fatalities in Alabama, California, Nevada and Texas.
The daily death tally is still well below levels seen in April, when on average 2,000 people a day died from the virus.
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