The US has recorded at least 94,000 new Covid-19 cases over the last 24 hours, with spikes in dozens of states days before the presidential election.
It is the second day in a row the country has broken its daily new case record after reporting more than 91,000 infections on Thursday.
More than nine million total cases have been reported in the US, according to a Johns Hopkins University tally.
The contest between Donald Trump and Joe Biden comes to a head on Tuesday.
Twenty-one states are experiencing outbreaks, with some of the most severe in the states that will be key in deciding the 2020 election.
In the battleground state of Wisconsin, hospitals in Green Bay warned that President Trump's Friday rally there could make the outbreak worse.
"It is more important now than ever to avoid large crowds, especially here in Green Bay, Wisconsin, where we are seeing some of the most rapid spread of Covid-19 in the United States," a joint statement from several hospitals said.
On Friday, ahead of his scheduled rallies, Mr Trump tweeted: "More Testing equals more Cases. We have best testing. Deaths WAY DOWN."
At recent Trump rallies, attendees have been screened and given masks. The events have also been held outdoors due to the pandemic. But there has not been social distancing, and some supporters continue to avoid masks.
Mr Biden has also continued to campaign, though the Democrat's rallies have enforced social distancing practices, opting to have people attend inside their cars, for example.
Mr Trump's eldest son, Donald Trump Jr, made an appearance on Fox News on Thursday where he repeated his father's line that the pandemic is under control.
"I went through the [Centers for Disease Control] data, because I kept hearing about new infections," the younger Mr Trump said.
"But I was like, 'Well, why aren't they talking about deaths?' Oh, because the number is almost nothing. Because we've gotten control of this and we understand how it works."
Johns Hopkins University says the US has reported more than 229,000 deaths due to Covid-19. The daily death toll has risen by more than 1,000 three days this month, according to Reuters news agency.
US health experts are warning the case load and death toll will continue to rise as the flu season coincides with the outbreaks.
Infectious disease expert and White House coronavirus task force member Dr Anthony Fauci told CNBC on Wednesday that the nation was "going in the wrong direction".
"If things do not change, if they continue on the course we're on, there's going to be a whole lot of pain in this country with regard to additional cases and hospitalisations and deaths."
Analysis - Naomi Grimley, Global Affairs Correspondent
Data from the US continues to shock the world. Total case figures are almost at the nine million mark, and the seven-day average is more than 75,000 new infections daily. Half of US states have seen new peaks in the last month.
There's been some talk of a "third wave" but many public health experts think that glosses over an inconvenient truth - that the US never really came out of the first one.
Whereas Europe's epidemiological graph looks like the cross-section of a valley between two peaks, America's looks more like a series of three steps. After the terrible spring when the virus was at its worst in the North East, such as in New York, cases did fall to around 20,000 a day across the country in early summer.
But then the Sun Belt states, such as Arizona, Florida and Texas, reopened for business and we saw surges begin there instead. Cases never had chance to drop to what Dr Fauci would have preferred - a base of something akin to 10,000 a day.
Now, after a bit of a fall at the start of September, cases are surging again. There's widespread transmission across the country, with states in the Midwest such as North Dakota, South Dakota, Wisconsin and Minnesota worst affected.