When sisters Nico, 6, and Nova, 4, get a little crazy, jumping off furniture, as kids will do while cooped up during quarantine, their parents, Megan and Charles Tran, have a running joke.

“You be careful now,” they tell the girls. “You kids can’t get hurt, because we’re not taking you to the emergency room during a pandemic.”

In fact, Megan Tran did take one daughter to the Children’s Hospital of Philadelphia emergency department last summer because of a severe stomachache — but not without hesitation. What Tran found when she got there was a waiting room with everyone spread out and parents huddled over their kids.

“I don’t think we’ve ever gone back to see a doctor so quickly during an emergency room visit,” Tran said.

The emptiness of CHOP’s waiting room that day was no fluke.

Emergency department visits locally dropped by more than a third last spring when COVID-19 first swept across the region, and still have not recovered fully. In the second half of 2020, they were 16% below their level the year before. The national picture looks no different, experts said.

What’s not clear, they said, is how many of the foregone visits should not have been skipped, leading to worsening illnesses or even death for individuals who feared contracting the virus at the ER.

CHOP saw the steepest decline among Philadelphia-area systems that reported the numbers on public financial disclosures. The number of visits to its emergency department plummeted 65% in the quarter ended June 30 compared with the one ended March 31. At the end of last year, they were still down 35%, compared with the year before.

The hospital attributed the decline to “a significant reduction in common viral infections and respiratory illnesses” caused in part by COVID-19 safety protocols, including physical distancing, masking mandates, and government stay-at-home orders.

CHOP’s assessment suggests that emergency-room visits will recover in a post-pandemic world — significant because CHOP is losing 5% to 6% of its revenue. But not all hospital executives are so sure that visits will rebound.

“We might have to reset what our expectations are,” Keith Kasper, chief financial officer of the University of Pennsylvania Health System, said last month while discussing the system’s 15% decline in emergency-department visits last year.

During a meeting of the budget and finance committee of Penn’s board of trustees, Kasper distinguished between trips to an emergency room that resulted in an admission to the hospital — down 2% last year — and those that did not — down 18%.

People with less severe ailments were still not showing up as much in January and February at Penn, Kasper said.

Tower Health saw a similar pattern, reporting a 3% decline in ER visits that turned into a hospital stay and a 23% decline by patients who were treated and discharged on the same day.

Where did those patients with less serious problems go? Penn, Tower and others saw huge increases in telehealth, which is appropriate for a portion of traditional ER visits, but it’s not clear how many trips to the ER were replaced by telephone and videos visits.

Penn said in a statement: “We are unable to pinpoint precise reasons for the decrease in lower-acuity visits. This is an important area of study and planning as we emerge from the pandemic and determine the continued role of telemedicine, remote monitoring, home care, and other methods of caring for our patients.”

Like other executives, Jack Lynch, Main Line Health’s chief executive is trying to figure out his system’s loss of ER visits. “I wouldn’t say we’ve seen an offset in our urgent-care centers to explain this,” he said.

Another possibility: “Did a bunch of people find a primary-care doctor and stop going to the emergency room? I don’t think that’s what happened,” Lynch said. ”I think people are afraid to go to the hospital, afraid to go to the emergency room.”

It’s also possible that fewer adults are being injured during weekend sports, and kids being schooled at home means fewer germs are being passed around.

Looming over the debate on the future of emergency departments is the worry that people have been dying of strokes or heart attacks because they were afraid of the hospital.

“I think it’s going to be kind of sobering when we hear the real results,” said Dan Grauman, chief executive of Veralon, a national health-care consulting firm with headquarters in Bala Cynwyd.

A study published last month in Journal of the American College of Emergency Physicians Open found that during last spring truly urgent ED visits dropped 30% in Louisiana. That was significantly less than the 50% drop in visits for care that were easily postponed, but still worrisome.

“There may be significant health consequences to avoiding emergency care for severe conditions, contributing to the estimated 87,000 excess non-COVID deaths thus far,” according to the study. Its lead author is Ari B. Friedman, an assistant professor of emergency medicine at the University of Pennsylvania. Friedman said he did not know of a similar study on the Philadelphia region.

Hospitals have complained for years about patients using their Emergency Departments for minor problems, or for primary care. If part of the decline in visits by people with conditions that are not severe turns out to be permanent, could that be a good thing for the health-care system as a whole?

“Then you don’t have patients that are clogging up the ED for services they could get somewhere else, and the only ones that are coming are the ones that need to be there,” said Brian Pisarsky, a senior vice president at Kaufman, Hall & Associates LLC., a Chicago health-care consulting firm.

“It’s a good question to be asked. In some of the EDs you sit for three to four hours for care. Now you might not need to do that,” he said.