The US death toll from Covid-19 passed 130,000 on Monday, with 44,361 new cases announced.
The US Centres for Disease Control and Prevention forecast that the death toll could reach 160,000 this month.
Over the past week, at least 32 states have seen surges in the number of infections as the virus count rises nationwide.
"Within a period of a week and a half, we’ve almost doubled the number of new cases," said infectious disease expert Dr Anthony Fauci, a leading member of President Donald Trump's coronavirus task force.
The US is averaging 20,000 new cases a day, Dr Fauci said.
"We are still knee-deep in the first wave of this," he said.
The country is nearing three million cases, or about a quarter of all known infections worldwide.
Dr Fauci expects there will be an answer before the end of the year or by early 2021 as to whether one of more than 140 experimental vaccines in development has proved safe and effective.
Any vaccine would probably be limited in how long it would shield against infection, he said.
A shot to protect against Covid-19 would not work like the measles vaccine, which lasts a lifetime, Dr Fauci said.
“We may need a boost to continue the protection but right now we don’t know how long it lasts.”
Meanwhile, Atlanta Mayor Keisha Lance Bottoms said on Monday that she tested positive for Covid-19, but had not shown symptoms.
Ms Bottoms gave no information about the diagnosis, whether she was under quarantine and when she was tested.
"Covid-19 has literally hit home," the first-term mayor of Georgia's state capital city said on Twitter.
Ms Bottoms is one of the women on the shortlist to become Democratic presidential candidate Joe Biden's running mate this year.
COVID-19 has literally hit home. I have had NO symptoms and have tested positive.
— Keisha Lance Bottoms (@KeishaBottoms) July 6, 2020
Florida's greater Miami area has became the latest coronavirus hot spot to return to lockdown, ordering all restaurant dining closed on Monday after 6,000 new Covid-19 cases were reported.
The surge in new cases has prompted many local leaders to slow easing restrictions or return to lockdown in the hope of curbing infection rates that have started to overwhelm hospitals in some areas.
Restaurants and bars were also singled out in California for increased coronavirus enforcement.
The state's hospital admissions for the respiratory virus have jumped 50 per cent in the past two weeks.
For an eighth straight day, Texas registered a new high in the number of people taken to hospital with Covid-19, up more than 500 admissions from the day before to nearly 8,700.
California, Texas and Florida are all among many states reporting increases in the percentage of Covid-19 diagnostic tests that come back positive.
Meanwhile, New York state officials confirmed that hospitals had released more than 6,300 recovering coronavirus patients into nursing homes during the height of the pandemic.
They said the controversial policy, which has been scrapped, was not to blame for one of the nation’s highest nursing home death tolls.
Governor Andrew Cuomo’s administration, which has taken intense criticism over the policy, said the virus’s spread through the state’s nursing homes was caused by more than 20,000 infected staffers.
It said many of them kept going to work unaware that they had the virus in March and April.
Another 17,500 workers were infected until early June.
