MIAMI — Inside a COVID-only intensive care unit at Jackson Memorial Hospital in Miami, all eight beds are filled with patients.

Six of the eight patients are younger than 50 years old. None of them has been vaccinated against COVID-19.

The youngest patient, a 27-year-old woman on a ventilator, had to be resuscitated with a bag valve mask after her blood oxygen saturation levels crashed. The oldest, a 71-year-old man, has been in the ICU for two weeks. He has been in a coma for three days. When he awakens, if he awakens, he will be a widower. The man’s wife, also hospitalized with COVID-19, died two days earlier.

Many health care workers at Jackson Memorial thought the end of the pandemic was in sight, largely due to the effectiveness of the vaccines. Then the delta variant took hold, particularly in areas with low vaccination rates, and cases are surging again, only at a faster clip.

“It just went boom,” said Ademola Ayo Akinkunmi, director of patient care services for Jackson Health.

Nurse managers and staff scrambled to create more space at Miami-Dade’s public hospital for the sudden rush of new patients, but they have struggled with what feels like a Sisyphean task.

“No matter how hard we work to discharge patients,” Akinkunmi said, “we know there are others coming.”

During the past month, the COVID-19 pandemic has roared back to life with astonishing speed and frightening virulence, crushing hopes for an end to the epidemic and presenting new challenges for public health officials.

New infections and hospital admissions are rising, driven by the highly contagious delta variant, relatively low vaccination coverage and the resumption of social activities.

At the same time, new evidence strongly suggests that even vaccinated individuals can catch and spread the virus — confounding public health officials struggling to persuade more Americans to get inoculated.

In Florida, the number of new cases and the rate of positive tests for the virus that causes COVID-19 — a measure known as the level of community transmission — is high in all 67 counties, according to Centers for Disease Control and Prevention data.

On Saturday, Florida reported 21,683 new COVID-19 cases as of July 30, the single-highest daily COVID-19 case count since the pandemic began 18 months ago, according to CDC data. The seven-day moving average soared to 15,817, a more than 750% increase since July 1.

The sudden and unexpected resurgence threatens the return to normalcy that many Americans have longed for after 18 months of the pandemic. Many felt they had done their part by getting vaccinated, but their resolve has turned to anger as they see that preventable disease and death is soaring, primarily among the roughly 50% of the nation that has not yet been vaccinated.

As cases surge, the daily count of total vaccine doses administered in the United States has plummeted from a seven-day rolling average high of 3.4 million in mid-April to fewer than 450,000 on July 29, according to CDC data.

“The vast majority of transmission, the vast majority of severe disease, hospitalization and death is almost exclusively happening among unvaccinated people,” CDC Director Rochelle Walensky said this week during a press call to announce that the agency had reversed its earlier recommendation that vaccinated persons did not have to wear masks indoors or outside because they were protected.

Walensky said new evidence had emerged that some vaccinated people infected with the delta variant may be contagious and spread the virus to others. “This new science is worrisome,” she said. But in announcing the update, Walensky did not provide evidence for the change.

The CDC’s about-face was sharply criticized as inconsistent and confusing by leading Republicans, including Gov. Ron DeSantis. Efforts to enforce the new guidance in the U.S. House of Representatives triggered a standoff, with some members refusing to wear masks as had been ordered by the Capitol Hill physician.

On Friday, the CDC released a new report of the agency’s investigation of an outbreak in Massachusetts during July. Investigators found that among 469 cases of COVID-19 linked to summer events and large public gatherings in Barnstable County on Cape Cod, nearly three quarters or 346 cases occurred in fully vaccinated individuals.

No deaths had been reported as of July 27, the CDC report said. But five people were hospitalized, including four who were fully vaccinated. One hospitalized patient between the ages of 50 and 59 was not vaccinated and had multiple underlying medical conditions. The four vaccinated patients ranged from 20 to 70, and two had underlying medical conditions.

The delta variant was the predominant strain in the outbreak, according to the report, which said that infection with delta led to similarly high viral loads in vaccinated and unvaccinated individuals.

“This finding is concerning and was a pivotal discovery leading to CDC’s updated mask recommendations,” Walensky said in a prepared statement on Friday. “The masking recommendation was updated to ensure the vaccinated public would not unknowingly transmit virus to others.”

Delta remains the dominant variant circulating in the United States, making up more than 80% of the virus samples genetically sequenced in recent weeks.

‘THIS IS VERY DIFFERENT’

For doctors, nurses, technicians, therapists and other health-care workers who have been caring for patients without a break since March 2020, the sudden surge has hurt morale, said Magdalena Nisr, a nurse manager for Jackson Health who works on the COVID-19-positive patient floor.

“It’s very depressing to see that as a community we’re going back to the numbers that we had at the beginning of the pandemic,” Nisr said.

Last summer, when Jackson Health was slammed with a surge of COVID-positive patients, hospital administrators suspended non-essential surgeries in order to open more beds. Most of the patients were elderly, and many had underlying medical conditions that raised their risk for severe outcomes from the disease, said Alix Zacharski, a nurse and manager of the medical intensive care unit at Jackson Memorial.

This time around, patients are younger, healthier and sicker.

“Unlike last year, we’re getting a very young population, which is extremely concerning because this time we’re now getting young people without pre-existing conditions,” Zacharski said. “So that’s scarier.”

On a recent weekday afternoon, Zacharski was working in the ICU when a 27-year-old patient’s vital signs crashed, triggering an alarm on a computer monitor in the nurses’ station. Her blood oxygen saturation levels had dropped suddenly from 95 to 64. Normal readings usually range from 95 to 100, and anything below 90 is considered low.

As the patient’s heart rate accelerated, Zacharski and her colleagues rushed to the patient’s room and removed the ventilator from her throat. Then they applied a bag valve mask, pumping the air bag by hand to force oxygen into the patient’s lungs.

The medical team revived the patient, and her blood oxygen levels slowly recovered. It’s possible that the patient’s blood oxygen levels crashed because of a mucus plug, Zacharski said, emphasizing that dangerous complications can arise at any time.

PATIENTS COMING IN MUCH SICKER

Many of the COVID-positive patients admitted in recent weeks appear to Zacharski to be more severely ill than those she saw last year.

“People come down with it within five days and they’re really sick,” she said. “They are coming to the hospital saying, ‘I don’t feel good. I can’t breathe’. That’s when you’re feeling, ‘Oh, this is very different from what it was before.’ ”

By the time a patient gets to the ICU, Zacharski said there’s not much more that nurses can do other than to help relieve the patient’s anxiety and get them to focus intensely on something most people do without thinking: breathe.

Doctors and nurses try mightily to avoid having to put a patient on a ventilator, she said, and every failure carries a heavy emotional burden.

“It’s very hard for us when someone’s eyes are looking at you, staring at you, deadlocked, pleading and begging you, hugging you to help them breathe,” Zacharski said. “That’s the part that stays with us. It’s really hard.”

PANDEMIC OF THE UNVACCINATED

The highest spread of new infections and severe illness is happening in places with low vaccination rates and among unvaccinated people.

Florida’s vaccination rate tracks closely with the nation’s coverage.

About 50% or 164.2 million Americans were fully vaccinated as of July 30, according to CDC data. In Florida, around half the eligible population 12 and older had not been fully vaccinated as of July 29, according to the state health department’s weekly COVID-19 status report, which counts 10 million fully vaccinated Floridians, or about 52.5% of an estimated 19.1 million eligible residents.

Miami-Dade has a relatively high vaccination rate — 85% of vaccine-eligible residents have received at least one dose and 70% were fully vaccinated as of July 29, according to the CDC.

Still, there are nearly 8 million Floridians who are eligible for the vaccine but have not taken it, said Jason Salemi, an epidemiologist with the University of South Florida in Tampa.

“Almost 1 million of those are people 65 and older,” he said.

Daily infections continue to increase across the country, with the seven-day rolling average now up to 67,080 new cases per day, nearly five times the most recent low on June 19, when there were 11,473 cases, according to the CDC. Florida infections were up to 15,817 cases per day, as per the seven-day rolling average the state reported to the CDC on Saturday— accounting for more than 1 in 5 of all cases reported in the United States.

Deaths from COVID-19 also have begun to rise nationally, with the seven-day rolling average up to 275 deaths per day, which is more than 60% higher than the most recent low of 170 deaths the CDC reported for July 10. Florida deaths have ticked up, too — rising to a seven-day rolling average of 43 per day on July 29 or more than 70% higher than the 25 deaths reported for July 10.

With rising infections come more COVID-19-related hospitalizations. Some of the fastest increases have occurred in parts of the country with low vaccination rates, including Florida, Nevada, Arkansas and Missouri.

In response, some Florida hospitals have suspended visitations and others have taken the more drastic step of restricting elective surgeries while administrators scramble to find space for intensive care patients and to shore up nursing and staffing shortages.

Brevard County’s Health First, which operates four hospitals, paused all elective surgeries not considered “essential” through Aug. 15 while Jacksonville’s Baptist Health asked surgeons to delay some elective surgeries at its six hospitals because of the rise in COVID-19 patients.

Orange County Mayor Jerry Demings this week announced that local hospitals are in crisis from the surge — one week after Miami-Dade Mayor Daniella Levine Cava issued a similar warning about rising hospital admissions, particularly among the unvaccinated, and urged everyone to get the vaccine to protect themselves and others.

On Wednesday, with cases and hospitalizations continuing to rise in Miami-Dade, Levine Cava mandated masks at all county facilities and urged businesses to require them indoors, too.

YOUNGER PATIENTS

Though hospital admissions continue to rise in Florida and elsewhere, they remain well below the peaks of spring and summer 2020. But there are notable differences between the patients admitted in recent weeks and those hospitalized during the waves last year.

Patients older than 80 are no longer the majority, as they were in 2020. Many more are middle aged and younger, reflecting a national trend. About 73% of patients hospitalized for COVID-19 were under the age of 65, according to CDC data as of the week ending July 24.

Dr. Marc Napp, chief medical officer for Memorial Healthcare System, the public hospital for South Broward, said patients are likely younger this time around because health officials emphasized the importance of vaccinating the elderly early on.

“It’s a good prediction that had we been more effective in getting the entire population vaccinated over the last six months, that we wouldn’t be where we are,” he said.

Memorial Health is now proceeding as though this July will be a repeat of last year, when COVID-19-related admissions peaked at 674 patients across the system’s six hospitals. The hospital system reported 420 patients with COVID-19 on Friday, including 55 who were in intensive care units. Only one person was vaccinated in the ICU, and 96% of the 420 were unvaccinated.

Administrators are hiring extra staff to handle increased patients, dialing back in-person meetings and reinforcing masking and social distancing.

“Any surge starts the way this surge is starting,” Napp said. “There’s no way to know how long it will last or how high it will go. … We are already preparing for being back where we were last summer.”

NEW MANDATES

Higher vaccination rates could have averted the current crisis, Walensky said when announcing the new CDC guidance, which calls for all Americans, vaccinated or not, to wear masks indoors in areas with high levels of community transmission. The CDC also recommends that everyone in K-12 schools wear masks indoors, including students, teachers, staff and visitors.

Walensky acknowledged the disappointment and fatigue that many may feel at having to take a step back at this stage in the pandemic, when there’s a vaccine that could help to end it but many have chosen not to take it. She said it was a difficult decision to reverse course.

People are tired, frustrated and many are facing mental health challenges, she said. But the continued pace of deaths, illness and hospital admissions for what is now a preventable disease demanded a change.

“It is not a welcome piece of news that masking is going to be part of people’s lives who have already been vaccinated,” Walensky said. “This new guidance weighs heavily on me.”

But growing frustration and anger has helped drive support for vaccine mandates.

On Thursday, President Joe Biden announced a requirement that all federal employees be vaccinated or face repeated tests and other restrictions. Biden, seeking to revive the nation’s stalled vaccination drive, also called on states to offer a $100 reward to individuals who get fully vaccinated.

The Department of Veterans Affairs became the first federal agency to mandate vaccination for employees while California and New York City announced requirements for their public workers to get vaccinated or submit to weekly tests.

The president’s announcement followed public calls this week by the American Medical Association, the American Hospital Association and other medical professional groups that all healthcare workers be vaccinated. Some Florida medical centers, including Holy Cross Health in Fort Lauderdale and the Mayo Clinic in Jacksonville, already require employees to be vaccinated.

At Jackson Health System, where about 60% of its 13,000-person workforce is vaccinated, CEO Carlos Migoya said he is considering a vaccine mandate. He acknowledged that the coverage rate for Jackson Health employees is “low” and said administrators were working to boost take-up of the shots and to dispel rumors and misinformation about the vaccine.

“Jackson employees are no different than every person out in the street,” he said.

‘GETTING SICK VERY FAST’

A big difference this summer is the delta variant, which appears to replicate much faster, with the virus becoming detectable four days after exposure compared with an average of six days in people with the original strain, said Dr. Lilian Abbo, an infectious disease specialist at Jackson Health.

“The people getting sick coming in now are getting sick very fast,” Abbo said. “We were not seeing that before.”

Abbo said vaccinated individuals also are testing positive and some develop symptoms, but that the vast majority are still protected from severe illness and even death from COVID-19.

“Vaccines work,” she said.

Napp, the chief medical officer for Memorial Health, said the vaccine is key to long-term control of the virus that causes COVID-19.

No matter which strain predominates, it is likely to become one of the thousands of viruses that circulate regularly, some of which can cause severe illness, such as the flu, and some that don’t, such as the common cold.

Once a person has been exposed to the virus, it’s possible that they will become infected again but the illness may not be as severe as the initial bout.

But for now, the virus has infected only a fraction of the population — meaning there’s a lot of wood left to burn. And first-time cases tend to be the most severe.

“Any virus that appears on the scene as this one has will be here forever,” Napp said. “It’s not going away. It’s going to be in the general circulation of viral pathogens.”

At Baptist Health South Florida, doctors expected an uptick in cases after the Fourth of July holiday. But the delta variant accelerated the rise to worrisome levels. COVID-19-related admissions have soared at Baptist Health — with 616 patients hospitalized across the nonprofit system’s 11 hospitals in Monroe, Miami-Dade and Palm Beach counties as of Friday.

Friday’s census of patients with COVID-19 at Baptist Health hospitals was a 58% increase over the prior week, and a 159% spike over two weeks ago.

Dr. Sergio Segarra said the high level of community transmission in South Florida is not just a statistic. It drives many more patients to the hospital and strikes people in all walks of life.

“The virus is rampant in the community and we’re seeing it in families. We’re admitting a husband and wife, a husband, wife and child,” he said. “All those things are happening.”

“We don’t have those elderly patients. It’s a younger population. So we’re often able to treat them as outpatients,” Segarra added. “But those that get admitted and get hospitalized are obviously a lot sicker. So even though they’re younger, they’re a lot sicker and unfortunately they can succumb to COVID as well.”

At Jackson Health’s three facilities in North Miami Beach, Miami and South Miami-Dade, COVID-positive patients are also rising and trending younger.

As of Friday, Jackson Health reported 232 patients admitted with COVID-19 — nearly four times as many as the 59 people hospitalized with the disease on July 1, but less than half the number of patients Miami-Dade’s public hospital saw at the pandemic’s peak on July 26, 2020, when there were 487 patients.

Nine out of 10 patients admitted with COVID-19 in recent weeks were not vaccinated.

HE DECLINED THE VACCINE

While the most severely ill patients at Jackson Health go to the ICU, there are more patients with milder symptoms from COVID-19 in the medical surgical wing.

That’s where Hialeah resident Victor Suero was recovering from COVID-19 on a recent weekday, in a section of the hospital called South Wing Seven.

Suero, 34, was admitted to Jackson Memorial on July 21 with a 102.5-degree fever and complaining of fatigue. Suero said he had chosen not to take the vaccine.

“I’ve had every opportunity to get vaccinated,” he said.

Suero, who works as a utility lineman, chalked up his hesitance to get vaccinated as, “just a personal preference.”

Then he said he had not taken the vaccine because he just moved back to Miami from Lancaster, Pennsylvania, where transmission of the virus was lower. Suero said he was also concerned that the vaccine might have an adverse reaction with medication he is taking to heal an infection in his left leg, which is still recovering from an open fracture that he suffered in a motorcycle accident in October.

Suero said he was not wearing a helmet at the time of his motorcycle accident, and that he considers himself “very lucky” to have avoided a serious head injury.

He said his mother and sister, who are vaccinated, have been urging him to take the vaccine, but he hadn’t listened. Suero said he doesn’t fall for disinformation, and acknowledged that perhaps his political preferences and a feeling of youthful invincibility may have something to do with it.

“It’s not from a lack of having it from both sides because I’m conservative, but at the same time my mom and my sister are both fully vaccinated. So they’re always bugging me about it, too,” he said. “Obviously, I don’t believe that if I get the vaccination I’m going to grow a third leg. It’s just that I’m a healthy male. I don’t really have any problems. Even for what I just went through, for me, it just felt like a really bad cold just with a fever. I know there are people who have it a lot worse than I do. But it was just a calculated risk on my behalf that I felt I would rather live with the consequences of being without it.”

Suero said he is reconsidering that decision now, in part because he fears what COVID-19 might do to his healing leg, which requires more surgery to repair the fractures.

“I don‘t want any complications with that. So that’s going to be more of the driving factor,” he said. “Because if they’re going to tell me something like, ‘Okay, well COVID is going to mess up my chances of saving my leg,’ then yeah, that’s going to be a simple answer to go get the vaccination.”

Miami Herald staff writer Sarah Blaskey, el Nuevo Herald staff writer Ana Claudia Chacin and Miami Herald newsroom developer Albert Franquiz contributed to this report.