ALLENTOWN, Pa. — By mid-January, the flu season at Lehigh Valley Hospital-Cedar Crest here in Allentown was bad enough to justify dragging out the "surge tent."
The Band Aid-colored structure in the parking lot — an inflatable military-style hospital ward a bit like a bouncy castle — is outfitted with cots, oxygen tanks and heart monitors.
Sandwiched between the ambulance helipad and the E.R. doors, the tent is mostly used as a holding area for walk-in patients who need monitoring. The extra space lowers the risk of infections in the main waiting room when the coughing and sneezing is at its worst.
Some 325 patients walked into the E.R. last Monday — "the record, as far as I can recall," said Dr. Andrew C. Miller, who runs the emergency department. The hospital admitted 108 patients.
"We thought this was peaking a week ago," said Dr. Miller. "It hasn't."
Thus far, he said, this has not been the worst flu season he's seen, but this year's seem sicker. It may yet get worse. The Centers for Disease Control and Prevention reported Friday that flu hospitalization rates across the country were the highest ever seen at this point in the season since tracking began in 2005.
The rates have already surpassed those of the 2014-15 season, when 710,000 Americans were hospitalized and 56,000 died. So far this year, 53 children have died; by the time the flu season ended in 2015, 148 children had died.
Infection rates are still rising, especially along the East Coast, where the flu arrived late. Hospitals are struggling.
The population near Lehigh skews older — a lot of retirement homes sit in these rolling hills — and the hospital is rated one of the state's top five, so ambulances often bring their sickest patients here, said Lindsay Houck, the emergency department's nursing director.
Normally, about a third of them need admission, she said, while hospitals nationally average about 12 percent. This winter, admissions here are creeping toward 40 percent.
At Lehigh, the most acutely ill bypass the tent and are wheeled deep into the hospital, sometimes to the one-bed isolation rooms that no one may enter without a mask.
Eric J. Scott, 68, a programmer at a tech company, was lying in one of those rooms. Sweat beaded on his forehead and ran down into his yellow surgical mask as he described the one-two punch that flu had given him.
"I've had it for about two weeks," he said. "I saw my doctor, and I felt like I was on the mend."
"But when I went to the grocery store, it just hit. My fever shot up to 101.9, and I got a real bad pain in my right side, my ribs. I felt like I'd been in a boxing match with my arms up — no defense."
Dr. Rafay Khan, who was treating him, said Mr. Scott might have coughed hard enough to crack a rib. He also had some pneumonia, which can cause flank pain, and would need his kidney function checked, too.
"I'm admitting him," Dr. Khan said. "He's over 65, and he's not eating or drinking — I can't send him home. He needs fluids and IV antibiotics and Tamiflu."
Mr. Scott said he usually got a flu shot at work but "I just didn't remember this year."
In the surge tent, Mark Moyer, 20, and Sarah Rogers, 22, were waiting for a note from Dr. Marna Rayl Greenberg.
Because of their hacking coughs, their boss at a local shipping warehouse had told them to leave and not return without a doctor's note.
But Dr. Greenberg, the hospital's vice chair of emergency medicine, produced notes certifying only that they were sick. "You need to be seen again, and then I can write you another one saying you're well," she said.
The couple, who had matching hand tattoos of the date they met, were clearly struggling. Their jobs pay only $9 an hour, and until they recently moved in with her parents, they had been living in a car.
"Missing work really sucks," Ms. Rogers said. "You have to pay your bills."
Financial need, medical experts say, plays a big role in spreading flu: many Americans go to work sick because they cannot afford to miss days. Mr. Moyer had been ill for two weeks.
"The chest pain is the worst part," he said. "I'm up till 2 or 3 coughing, and I got to get up at 6 to go to work."
Ms. Rogers had been sick for five days. Because she used an inhaler, Dr. Greenberg offered her a prescription for Tamiflu, even though it normally is effective only within the first two days of infection.
Ms. Rogers' head jerked back. "No, I heard it causes hallucinations," she said. "I heard about a lady whose daughter got Tamiflu and tried to kill her."
Dr. Greenberg tried to reassure her that the rare side effects were more likely to be nausea or diarrhea — and then asked if she got flu shots.
"I hear the shot gives you flu," said Ms. Rogers. "I heard you can get Alzheimer's from it — that there's mercury in it, and it goes to your brain."
Mr. Moyer interrupted to ask Dr. Greenberg what caused flu, and Ms. Rogers interjected: "I heard it's a government plot for population control."
Asked where she got such ideas — which contradict everything medical experts teach — she shook her head ruefully and appeared to smile behind her mask.
"I'm a hypochondriac," she said. "Social media is the worst thing."
Without directly contradicting her, Dr. Greenberg gently tried to change her mind about Tamiflu and the shot — to no avail.
Dr. Luther V. Rhodes III, the hospital's chief epidemiologist, said he, too, was frustrated by the flaws of the vaccine, which is expected to be only about 30 percent effective this year.
"Even in a good year, it's a C-plus, B-minus match, and even the high-test stuff for old people is a joke," Dr. Rhodes said.
"Tell Tony Fauci to stop saying we need a universal flu vaccine and just do it," he added, referring to the director of the National Institute of Allergy and Infectious Diseases. "We need a Kennedy-esque go-to-the-moon project."
Despite the vaccine's imperfections — and the rumors it inspires — Lehigh does everything it can to get people to take it. In the fall, after the local baseball stadium and amusement park close, the hospital holds free drive-through "flu shot days" in their parking lots.
"We can handle 15 lines of cars," Dr. Rhodes said. "We gave away 11,000 shots last year. That will definitely save a number of lives. People who would be in our E.R. will be home watching the Super Bowl."
Upstairs in the pediatric ward at Lehigh Valley Hospital, 12-year-old Ethan Lasorsa, a quick-witted, cheerful Philadelphia Eagles fan and holder of a second-degree black belt in kyokushin karate, was being released after two nights in the hospital.
"We thought he had strep throat — he gets it pretty regularly," his father, Travis Lasorsa, 41, said. "But on Sunday afternoon, it went from 'He's going to be fine,' to 'We're scared.' He had 102.9 fever, he was really pale and he couldn't breathe."
Ethan did not have strep throat; he had an ear infection and the flu, said Dr. Kristen Prendergast.
He, too, had not had a flu shot.
"As a family, we don't get it," said his father, a Dun & Bradstreet sales manager, explaining that he and his wife, Nicole, felt they had previously gotten the flu more often in years when they got shots. "This is the first time we didn't get it and got the flu."
Experts say the vaccine, which contains killed virus or just viral particles, cannot cause flu.
Ethan could name every drug he'd been given, but shook his head emphatically when asked if he might want to be a doctor someday.
"I don't like being in the hospital," he said. "What have I learned? That this is a harsh virus."
An earlier version of this article misstated the reason that Ethan Lasorsa, a pediatric patient, was hospitalized. In addition to the flu, he had an ear infection, not strep throat. The article also misstated the number of hospitalizations in