Millions of Americans marked a very different Independence Day this year, with many choosing virtual celebrations or canceling plans altogether amid mounting concern over the coronavirus pandemic.

The changes followed pleas from health officials warning that holiday crowds and packed gatherings like the ones the U.S. witnessed over Memorial Day weekend would likely lead to further spikes in coronavirus cases.

Nearly half of U.S. states have halted their reopening plans as new coronavirus cases surged to record-breaking numbers in recent weeks.

Both city and state leaders attributed part of that rise to gatherings -- particularly among younger people.

At least 19 states now have mask mandates to help curb the spread of infections as new research suggests a new form of the virus has spread from Europe to the U.S.

The mutation makes the coronavirus more likely to infect people but doesn't make patients any sicker than previous variations.

The U.S. Centers for Disease Control and Prevention is now projecting the country will see nearly 148,000 coronavirus deaths by the end of the month. So far, at least 129,718 Americans have died and more than 2.8 million have been infected, according to Johns Hopkins University.

And while many cities took measured approaches to celebrate the Fourth of July, images emerging from the holiday weekend show not everyone is taking the warnings seriously.

Fourth of July crowds

Crowds flocked to Virginia Beach shores Saturday, even after the city canceled its holiday fireworks display to "help keep Virginia Beach safe in the face of the coronavirus pandemic." CNN affiliate WAVY reported city officials warned residents of additional traffic because of the holiday, adding they anticipated tens of thousands of people would visit Virginia Beach.

Rehoboth Beach, Delaware, saw similar scenes as beachgoers opted to celebrate by the water Saturday. Earlier this week, the state's governor announced bars at Delaware beaches would be closed for the holiday weekend.

Meanwhile, in California, where many beaches in the southern part of the state closed for the holiday weekend, the beach crowds in San Diego were reminiscent of years past. CNN affiliate KSWB reported many were not social distancing or wearing masks.

"It seems pretty regular for the Fourth of July with definitely a lot of people," Marine Safety Lt. Rich Stropky told the affiliate.

Masks and social distancing were also features that were mostly absent from the White House Fourth of July celebration. Tables on the White House South Lawn were somewhat spaced, with about six chairs per table.

And as people tried to beat the July heat, many congregated in the shady areas of the space, not distancing at all.

FLORIDA SETS ALL-TIME RECORD

Florida reported 9,999 new coronavirus cases Sunday. That came one day after the state set an all-time record of most cases in a single day with a total of 11,458 new cases, according to data from Johns Hopkins University.

The state has now surpassed New York's previous single-day high of 11,434, which was recorded in mid-April.

Despite the rapid rise in cases and officials' warning Florida may be the nation's new epicenter, the governor has said he's not planning on walking back reopening measures.

Miami Beach Mayor Dan Gelber told CNN that hospital capacity in his city is dropping. In the last two weeks, he said, hospitalizations have doubled.

"Too many people obviously are not taking seriously at all these admonishments to socially distance, to wear masks, all those things," Gelber said.

On Sunday, FDA Commissioner Dr. Stephen Hahn said on CNN's "State of the Union" that it was "too early to tell" if it would be safe for the GOP convention to be held in Florida next month.

"We'll have to see how this unfolds in Florida and around the country," said Hahn, a member of the White House Coronavirus Task Force.

Much of the convention is set to be held in Jacksonville, which was chosen by the President's re-election team after sparring with North Carolina officials over social distancing requirements. The convention was initially to be held in Charlotte, but now only a small part will take place there.

34 STATES RECORD RISE IN NEW CASES

Coronavirus cases are on the rise in 34 states over the past week, with 12 recording an increase of more than 50%, according to data from Johns Hopkins University. Three states -- Kentucky, New Hampshire and Vermont -- are reporting a decline in cases.

These are the states where cases are trending up: Alabama, Alaska, Arizona, California, Colorado, Delaware, Florida, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Louisiana, Maine, Maryland, Michigan, Missouri, Montana, Nevada, New Mexico, North Carolina, North Dakota, Oklahoma, Ohio, Oregon, Pennsylvania, South Carolina, Tennessee, Texas, Washington, West Virginia and Wisconsin.

"We opened way too early in Arizona," Phoenix Mayor Kate Gallego, a Democrat, told ABC's "This Week" on Sunday. She attributed much of the "explosion" in cases to people between the ages of 20 and 44.

"We're seeing a lot of people go to large family gatherings and infect their family members," Gallego said.

In Texas, there were 8,258 new cases of Covid-19, according to the latest data released by the Texas Department of State Health Services (DSHS). That marks the second highest number of cases reported in a day from the state. The previous record was set on July 1, when there were 9,308 new cases reported.

Hospitals in at least two Texas counties have hit their maximum capacities.

In Starr County, at least two patients had to be flown out of the area for treatment.

"The local and valley hospitals are at full capacity and have no more beds available. I urge all of our residents to please shelter-in-place, wear face coverings, practice social distancing and AVOID GATHERINGS," Judge Eloy Vera said.

In Hidalgo County, Judge Richard Cortez asked residents to shelter in place and "only call 911 if absolutely necessary."

Cases are steady in 13 states: Arkansas, Connecticut, Massachusetts, Minnesota, Mississippi, Nebraska, New Jersey, New York, Rhode Island, South Dakota, Utah, Virginia and Wyoming.

121 COLLEGE STUDENTS TEST POSITIVE IN WASHINGTON

Outbreaks have been popping up around the country, including at the University of Washington in Seattle, where 121 students tested positive, according to a joint press release from the university and Public Health Seattle & King County.

Of those, 112 are residents of fraternity houses on Greek Row in the north section of campus, the release said. Students who tested positive but are not residents of the houses are close contacts.

On July 3, the student-led governing board for UW fraternities reported that at least 117 residents living in 15 fraternity houses self-reported positive tests, the release said.

News of the infected students could signal what many colleges across the country face as they prepare for the fall semester and outline plans for on-campus housing.

In north Georgia, an unspecified number of counselors and campers from summer camps have tested positive for Covid-19 after one counselor was first confirmed positive on June 24, according to Lauren Koontz, CEO and president of the YMCA of Metro Atlanta. The counselor was immediately sent home and both locations for Camp High Harbour were closed.

"We have since learned of additional positive Covid-19 test results of campers and staff," Koontz said in a statement, "but cannot confirm a number."

Koontz pointed out that while preparing for camp, the YMCA of Metro Atlanta collaborated with the CDC and the American Camp Association, in addition to following guidance outlined by the state.