Florida set a grim daily record for deaths from the coronavirus, with 156 announced on Thursday.
The state’s department of health reported 13,965 new cases, bringing the state's total throughout the pandemic to almost 316,000.
The US Department of Labour also reported a surge in first-time filings for unemployment benefits in Florida, which has recently emerged as a hot spot for Covid-19.
In the week ending July 11, there were 129,408 new filings, an increase of more than 62,000 from the week before.
In California, two more school districts, San Francisco and Sacramento, announced that public school students will not return to classrooms when the new term begins.
The decision was prompted by surges in coronavirus cases and delays in getting test results back.
They join Los Angeles and San Diego, the state’s two largest school districts.
Other schools staying closed include those in Oakland, Long Beach, Santa Ana and San Bernardino.
They have chosen to start the autumn term with online learning amid strong concerns from teachers' unions and public health officials about the safety of schools.
State officials expect more districts to announce plans for distance learning.
The Centres of Disease Control and Prevention on Thursday reported 67,404 new coronavirus infections nationwide, bringing the case count to 3.4 million.
The number of deaths rose by 947 to 136,938.
Meanwhile, mayors in Atlanta and other Georgia cities hardened their defiance against Governor Brian Kemp after he banned cities and counties from making face coverings obligatory.
Mr Kemp said municipalities did not have the power to order the use of masks in public places.
Democratic local officials condemned his stance.
Savannah Mayor Van Johnson, who on July 1 became the first to defy Mr Kemp by ordering masks to be worn, took to Twitter on Wednesday night to blast the governor.
Officials in at least 15 Georgia cities and counties, including Atlanta Mayor Keisha Lance Bottoms, ordered masks to be worn in public during the coronavirus pandemic.
Many are expressing outrage at Mr Kemp for trying to stem their efforts.
Meanwhile, the US announced that borders with Mexico and Canada would stay shut for most travel until August 20 to stem the spread of the coronavirus.
In Canada, the leaders of several provinces spoke out against reopening the border with the US because of its surge in cases.
Canada has recorded more than 8,800 deaths and more than 108,000 cases, while Mexican cases have topped 317,000 and the number of deaths is nearing 37,000.
The leading US expert on infectious diseases, Dr Anthony Fauci, predicted on Wednesday that the country would meet its goal of a coronavirus vaccine by the end of the year.
"I feel good about the projected timetable," Dr Fauci told Reuters.
His comments follow promising early-stage data for Moderna's coronavirus vaccine, released on Tuesday, that was developed with scientists at the National Institute of Allergy and Infectious Diseases, of which Dr Fauci is director.
Many experts see a safe and effective vaccine as the only way out of the pandemic, which has infected 13.8 million and killed almost 590,000 people worldwide.
Dr Fauci said Moderna's results were especially promising because the vaccine appeared to offer the type of protection seen in a natural infection.
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A Walmart shopper wears a mask as protection against the coronavirus as he leaves the supermarket in Burbank, California. The retailer announced it will require customers nationwide to wear face masks inside their stores from July20. EPA -
A woman wearing a face mask walks past graffiti that promotes social distancing amid the ongoing coronavirus pandemic, in Kibera, Nairobi. AFP -
A man comforts his son after taking a coronavirus test in Getaria, Basque Country, Spain. The Basque health department has set up a text campaign in the town to try to control a possible coronavirus outbreak in the area. EPA -
A street musician wears a cloth over his face as protection amid the coronavirus pandemic as he plays his saxophone for tips in La Paz, Bolivia. AP Photo -
Passengers sit, separated from their neighbours by a curtain, on a bus amid the coronavirus pandemic, in Lima, Peru. Reuters -
People wearing face cover cast their vote at a polling station during the general election in Skopje. North Macedonia went to the polls on July 15, 2020 to elect a new parliament. AFP -
Doctors and nurses wearing personal protective equipment look after a coronavirus patient at the intensive care unit of the Sharda Hospital, in Greater Noida, in northern India. AFP -
Children attend a tele-learning class at their home displayed on Kalvi TV channel, an education tele-learning initiative set up by the department of school education, amid the coronavirus pandemic in India's southern city of Chennai. AFP -
A resident sits inside her home in the city of Navotas, Manila, before a lockdown to contain the coronavirus pandemic in the Philippines got under way. The infections continue to rise in the country after reopening the economy suffering a twin blow of recession and the pandemic. AP Photo -
People spend the afternoon on Playa del Salado beach in Caimito, Artemisa province, Cuba. With government restrictions easing and a heatwave sweeping the island, Cubans are packing the beaches without face masks. The coronavirus infection rates in the country remain low. AP Photo -
A canine training official shows a dog trained to detect Covid-19, during a demonstration to the press, in Santiago, Chile. EPA
