Deaths and hospitalizations are rising as well.
The outbreak is hitting in record numbers nationwide -- but the virus is spreading faster in cases per population in many hotly contested states, including Florida, Georgia, Iowa, Minnesota, Michigan, North Carolina, Nevada, Ohio, Wisconsin and Texas, according to the analysis of data from Johns Hopkins University.
And Georgia, which has emerged as a competitive state, is experiencing a "surge."
"Winter is coming," said Dr. Lynn Paxton, the health director in Fulton County, Georgia. "We are clearly experiencing a surge in infections in Georgia."
Exactly how the most recent rise in cases in key swing states, which began earlier this fall, will ultimately impact the presidential election remains unclear, but experts said its effects have already been felt. Many say the surge in cases is likely to hurt the president at the ballot box, though a Trump's campaign official Sunday suggested it may be to their advantage to have Democrats talking about it so much, as fear over the outbreak could prevent those more likely to support Biden from turning out on Election Day.
Record numbers of mail-in ballots have been requested, though, and early voting is smashing total tallies from 2016 and fears of getting the virus do not appear to be suppressing the drive to vote in person, even in places where cases are surging, experts said.
So the story of coronavirus in key swing states may be less of a case of what happens on Election Day than what preceded it.
How the pandemic may be affecting the race
For Trump, who has faced heavy criticism for his handling of the pandemic, the spike could continue to hurt his effort to shift focus to other topics and downplay its gravity.
Trump has repeatedly argued that the U.S. is "rounding the turn" with the virus, that a vaccine is "weeks away," that the virus is not serious for the vast majority of people and other such claims. He and his supporters have also stressed that lockdowns associated with the virus, mainly in Democratic-led states, are doing more damage than the disease itself.
An ABC/News Washington Poll last week found that more than 6 in 10 Americans disapprove of the president's response to the pandemic.
"If this election is about Trump's handling of the pandemic, he's going to lose," Alex Conant, a political consultant and longtime Republican communications strategist who most recently worked on Marco Rubio's 2016 presidential campaign, told ABC News.
"The biggest problem for Trump is all these headlines are keeping the pandemic front and center, when he wants to change the focus to the economy and Biden's shortcomings," he said.
But the rise in cases does not appear to be preventing voters from casting ballots, using mail, drop boxes, or early voting locations across the country.
More than 93 million people have already voted as of Sunday, according to data compiled by the U.S. Elections Project, with numerous states getting closer to breaking records ahead of Election Day.
Only 136.7 million votes were cast in 2016, according to the Federal Election Commission, so it's still unclear how many people will vote on Election Day.
Experts simply don't know if the pandemic will impact Election Day turnout for in-person voters.
"Certainly it makes intuitive sense that there could be a connection, but I just don't know for sure," said Kyle Kondik, an analyst at the University of Virginia Center for Politics.
Some Trump counties in key swing states suffering
Though there is no clear correlation between the rising infection rates and the politics of a particular region, the numbers show that over the past two weeks, cases overall have risen faster in key counties won by Trump in 2016. In battleground states, Trump counties reported an average of 309 cases per 100,000 in the last two weeks, compared to 258 cases per 100,000 reported in counties won by Clinton.
In Iowa and Minnesota, the 10 counties with the highest infection rates as of last week were won by Trump in 2016.
In Wisconsin, nine of the 10 counties with the worst outbreaks were counties where Trump prevailed.
Since the spring, the virus has changed course in the U.S.
Coronavirus first decimated the heavily Democratic Northeast. After that it morphed into a more pervasive, but less deadly outbreak in the South in the summer.
The latter coincided with states reopening despite virus cases surging and the increasing politicization of masks and other mitigation measures.
And finally, the virus hit the rural areas that had largely been spared in the first two surges.
Despite the latest surge in the virus, the country has avoided the widespread lockdowns that characterized the spring.
"No question, if the coronavirus somehow magically never happened, this would be a very different election," Bill McInturff, a Republican pollster, said on NBC on Sunday.
Jason Miller, a senior political adviser for the Trump campaign, said he believes Democrats could be suppressing turnout for their own voters by spending so much time emphasizing the virus.
"The thing that I would point out here that I think is really going to backfire on Democrats and many in the media is the Democrats have spent so many months telling folks that it's not safe to go out and vote in person on Tuesday," Miller said Sunday on ABC's "This Week." "There's been so much media pressure effectively putting out scare tactics to keep folks away. Well, guess what? President Trump supporters are going to show up on Tuesday. Nothing is going to stop them."
The virus expanded voting well beyond Election Day
In many states, the efforts to expand voting options ahead of Election Day appears to have already helped voters find safer routes to cast their ballots in the face of coronavirus risks.
"States have done a good job of creating an alternative to in person voting," Conant said. "Across demographic groups, we're seeing high turnout, including areas that have spikes in the pandemic."
In Sheboygan County, Wisconsin, another Trump county suffering from one of the worst rates of COVID cases in the state, County Clerk Jon Dolson told ABC News that "several municipalities had lines of people on the first day of in-person absentee voting," mostly of people who didn't want to stand in line on Election Day, even though "with all of the absentee voting, there won't be lines on election day."
In Texas, which is considered to be competitive for Joe Biden, cases are "rising quickly," according to the state health department, with the state averaging over 6,000 new cases per day in the last week. However, election officials say the rise in cases has not deterred voters from casting their ballots at the polls, or by other more unconventional methods, such as drive-thru voting. On Sunday, the Texas Supreme Court denied a petition by a group of Republicans, who sought to invalidate nearly 127,000 drive-thru votes in Harris County.
In fact, while the seven-day average of new cases in El Paso has surged by more than 550% just in the last month alone, voter participation has actually gone up.
People are "overcoming the fear of COVID-19 to go out and vote," said Antonio Rivera, assistant elections administrator for El Paso County.
Texas has already cast well over the number of votes that it did in 2016, according to the U.S. Elections Project, and several states are close to exceeding their total for that year as well.
Health and election officials across the country have made extensive preparations to ensure safe in-person voting in the midst of a once-in-a-century pandemic. Many are providing workers and voters with personal protective equipment (PPE) and hand sanitizer, and nearly all health officials ABC News spoke to last week feel their state can conduct elections in a safe manner. At least 33 states will ask voters to wear masks at polling locations, according to an ABC News survey.
In Wisconsin, where experts said COVID-19 hospitalization could double in the next 2-6 weeks, hospitalized or quarantined patients are being asked to designate an agent to pick up and drop off their ballots.
Shauntay Nelson, the state director of All Voting is Local, a progressive group working to get out the vote in Wisconsin, told ABC News that the coronavirus has motivated voters in the state even more.
"I've driven around to some of the early voting sites, and I've seen an energy and an excitement especially among Black and brown people," Nelson said.
"What I've noticed is a tenacity to not be denied the power to vote, a tenacity from people who have been suppressed for years and years, who are making a decision to say I will not allow any form of suppression to stop my vote."
ABC News' Laura Romero and Arielle Mitropoulos contributed to this report.