◆ U.S. cases near 5 million.

BOSTON — Fourth of July gatherings, graduation parties, no-mask weddings, crowded bars — there are reasons the U.S. has racked up more than 155,000 coronavirus deaths, by far the most of any country, and is fast approaching an off-the-charts 5 million confirmed infections, easily the highest in the world.

Many Americans have resisted wearing masks and social distancing, calling such precautions an overreaction or an infringement on their liberty. Public health experts say the problem has been compounded by confusing and inconsistent guidance from politicians and patchwork approaches to containing the scourge by county, state and federal governments.

“The thing that’s maddening is country after country and state after state have shown us how we can contain the virus,” said Dr. Jonathan Quick of the Duke Global Health Institute. “It’s not like we don’t know what works. We do.”

Confirmed infections in the U.S. have topped 4.7 million, with new cases running at more than 60,000 a day.

While that’s down from a peak of well over 70,000 in the second half of July, cases are on the rise in 26 states, many in the South and West, and deaths are climbing in 35 states.

On average, the number of COVID-19 deaths per day in the U.S. over the past two weeks has gone from about 780 to 1,056, according to an Associated Press analysis.

In Massachusetts, health officials are investigating at least a half-dozen new clusters of cases connected to such events as a lifeguard party, a high school graduation party, a prom party, an unsanctioned football camp and a packed harbor cruise trip.

One recent house party on Cape Cod attended by as many as 60 people led to more than a dozen new cases and prompted some restaurants to close or limit service at the height of tourist season.

Hot spots around the U.S. are popping up in what once seemed like ideal places to ride out the outbreak: rural, less populated and with lots of outdoor space.

In South Dakota, a spike erupted at a Christian youth summer camp in the Black Hills, with cases growing to 96 among 328 people who attended.

“We’re at a point where there’s enough spread of COVID-19 that people throughout the U.S. are at an increased likelihood of encountering the virus and getting exposed,” University of Florida epidemiologist Dr. Cindy Prins said.

She added: “This is a behavioral disease right now for a lot of people.” Prevention means “changing our behavior, and it’s so hard for humans to do. We’re social creatures.”

In Mississippi, Republican Gov. Tate Reeves grudgingly reversed course and announced a statewide order requiring the wearing of masks because of a resurgence of the virus. He also delayed the start of the school year for upper grades in eight hard-hit counties.

“Wearing a mask — as irritating as it can be, and I promise you I hate it more than anyone watching today — is critical,” he said.