(CNN)As Americans find some beaches closed and Fourth of July fireworks scarce, authorities fear the holiday weekend may worsen the already ravaging coronavirus pandemic.
More than two months after the first peak affected just a handful of states, the virus is cresting again across the South and Southwest.
The US reported Friday at least 51,842 new cases, marking the third day straight with a daily high of more than 50,000 cases, according to data from Johns Hopkins University.
Those who have not given up celebrating America's independence outdoors are finding that beaches in Miami and Los Angeles have been closed, tubing in Texas rivers has been banned and city-sponsored celebrations will be live-streamed.
After crowds were gathering at Myrtle Beach, South Carolina, on Friday, Mayor Brenda Bethune said officials were working to get the message out that masks are needed.
"People spread this virus and we can't stop people from coming here but we all have personal responsibility in helping to prevent the spread of this virus," Bethune told CNN's Jim Acosta.
California, Arizona, Texas and Florida all posted record new cases this week -- Florida reported nearly 9,500 additional coronavirus cases on Friday. Texas had 7,555 new cases after back-to-back days with about 8,000 a piece.
Florida is averaging more new cases per day -- 7,870 -- than any other state, according to a CNN analysis of data from Johns Hopkins University. California and Texas trail close behind.
"There's nothing more American than making a sacrifice by staying home to keep a family member safe, a neighbor safe or a stranger safe," Miami Beach Mayor Dan Gelber told CNN.
Nearly two dozen states have paused their reopenings to combat the spread while others have taken extra measures to keep it out of their borders. New York, New Jersey and Connecticut issued a travel advisory that requires people arriving from eight states with high coronavirus rates to quarantine for two weeks.
Here are other significant developments this week:
A man and a girl hear a band outside a music venue in Nashville, Tenn. The Nashville Health Department has a mask mandate to help battle the spread of the coronavirus.
Masks alone cannot help combat coronavirus
Some state leaders and experts have blamed the spike in cases on more testing.
"What we're seeing now in the Southwest is a surge in both the number of positive cases and the percentage of people testing who are positive," Dr. Jonathan Reiner, a CNN medical analyst and professor of medicine at George Washington University, said on Friday.
But others experts attributed it to a lack of a comprehensive response.
"If you turn your back on the virus, if you turn your back on science, it's going to bite you," said Dr. Thomas Frieden, the former director for the Centers for Disease Control and Prevention.
More of CNN's coronavirus coverage
The virus, he told CNN, cannot be stopped by a single measure.
"Whether it's restricting travel or staying home or testing a lot of people or wearing a mask. And those are all important, but none of them, in and of themselves are going to control this," he said.
Officials fear July Fourth could bring a surge in cases, and are urging Americans to limit their festivities. The holiday weekend could be the "perfect storm" for new cases, said Dr. Joshua Barocas, an infectious disease physician at Boston Medical Center.
Coronavirus has killed more than 129,000 people and infected over 2.7 million nationwide, according to Johns Hopkins University. As infection rates continue rising in 36 states, the Centers for Disease Control and Prevention is projecting nearly 148,000 deaths in the US by the end of the month.
No social distancing at President Trump's event
The President and first lady Melania Trump went to Mount Rushmore National Memorial on Friday for an early Fourth of July celebration expected to be attended by 7,500 people.
No social distancing is planned for the event.
"We told those folks that have concerns that they can stay home, but those who want to come and join us, we'll be giving out free face masks if they choose to wear one," Republican Gov. Kristi Noem told Fox News.
CNN medical analyst Dr. Celine Gounder said holding such an event during a pandemic is "beyond irresponsible."
"This is the behavior of a cult leader who is jumping off the cliff but he is jumping into a safety net -- with protections around him," she said of the President. "While he asks the followers to jump off a cliff into nothing."
Coronavirus cases in South Dakota currently remain stable, according to data from Johns Hopkins University, with 6,893 confirmed cases and 97 deaths as of Thursday. But it's unclear how many attendees will travel from other states.
One Michigan bar. At least 158 coronavirus cases
It started with two cases traced to one bar in East Lansing, Michigan, a couple of weeks back.
Now, at least 158 coronavirus infections have been linked to that bar, Ingham County Health Officer Linda Vail told CNN on Friday.
Crowding, shouting, long lines and drinking combined to create "a perfect storm," she said.
"It's really hard to contain when young people are reckless and don't think it's going to affect them, much less those high-risk people around them," Vail said.
Virus has mutated to become more infectious
The warnings of health officials are especially relevant following new research that the virus has mutated to become more infectious.
A global study found strong evidence a new form of coronavirus has spread from Europe to the US. The new mutation makes the virus more likely to infect people but does not seem to make patients any sicker than previous variations, according to an international team of researchers.
"It is now the dominant form infecting people," said Erica Ollmann Saphire of the La Jolla Institute for Immunology and the Coronavirus Immunotherapy Consortium, who worked on the study. "This is now the virus."
The study was published in the journal Cell.
US to be placed on UK travel 'red list'
The UK government is expected to designate the United States as a "red list" travel destination due to concerns over the soaring US infection rate, UK Transport Secretary Grant Shapps said.
"Here, we've got things under control, but we know [the virus] is still raging in parts of the world, Shapps told BBC Radio 4. "So, I'm afraid there is a red list."
"The US, from a very early stage, banned flights from the UK and from Europe, so there isn't a reciprocal arrangement in place," he added, noting the US still has a "very high" rate of infection.
Thousands more deaths projected this month
The CDC now projects nearly 148,000 coronavirus deaths in the United States by July 25.
Surgeon General Dr. Jerome Adams urged caution about the death rate for the virus remaining flat while the number of new cases increases.
"We know deaths lag at least two weeks and can lag even more," Adams said Friday on "Fox & Friends."
"In the beginning, nursing homes were hit really hard, and the majority of our deaths were occurring on people who were 60, 65 and older. Now the majority of cases are in people who have an average age of 35."
He added, "What we're really worried about -- particularly with young people -- is that they get it and then they spread it to their grandmother, to their grandfather."
The new projections estimate a range of 139,000 to 161,000 deaths.
"The state-level ensemble forecasts suggest that the number of new deaths over the next four weeks in Arizona, Arkansas, Florida, Idaho, Nevada, Oklahoma, Oregon, South Carolina, Texas, Utah and Wyoming will likely exceed the number reported over the last four weeks," the CDC said.
More states make sweeping mask mandates
When mask mandates for Texas and Kansas go into effect Friday, 19 states and Washington, DC, will have such requirements.
In a major change, Texas won't allow people who are in counties with 20 or more active Covid-19 cases to go out without a face covering. That's about 95% of Texans.
"We have the ability to keep businesses open and move our economy forward so that Texans can continue to earn a paycheck, but it requires each of us to do our part ... and that means wearing a face covering in public spaces," Texas Gov. Greg Abbott said.
On Friday, cell phones in the state received an alert advising people to wear masks in public spaces.
"Punishable by a $250 fine," the alert read.
Other governors have also issued statewide orders, including California, Connecticut, Delaware, Hawaii, Illinois and Michigan.
The cause of the current spike in cases is impossible to pinpoint, said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. But a series of events that occurred simultaneously, including protests, Memorial Day festivities and states reopening, likely contributed, he told the Harvard Business Review.
Of the 36 states whose new cases have gone up this week compared to the previous one, nine of them have increased by over 50%. They are Montana, Idaho, Nevada, Florida, Georgia, Tennessee, Louisiana, Alaska and Delaware.
