The seven-day average of new coronavirus cases in Philadelphia is the highest it has ever been as both the delta variant and the extremely transmissible omicron variant spread through the region.

The city was averaging 1,407 new cases per day as of Monday, surpassing the previous record of 1,235 set on Dec. 8, 2020. The number has shot up in recent weeks, increasing fivefold since Nov. 30.

“The concern’s high,” said Patrick Kelly, an intensive care unit nurse at Einstein Medical Center, which is already near capacity with sick patients. “More people are in contact with people who are positive. It’s the same thing with everyone you talk to.”

City officials say they believe cases will continue to increase in the days and weeks to come. Most of these new cases were reported in the days leading up to Christmas, when many people attended gatherings.

“Places like the United Kingdom and Denmark are still seeing rapidly rising cases,” said James Garrow, a spokesperson for the Philadelphia Department of Public Health. “They started this rise before we did, so we figure there is still some time before we reach that peak.”

A vaccine mandate goes into effect in Philadelphia on Jan. 3 for all businesses that serve food, but no additional restrictions are currently planned, Garrow said.

Since hospital surges typically lag weeks behind case surges, several experts and officials said they won’t know until mid-January whether hospitals here become overwhelmed.

“We don’t have a sense of when hospitals will reach a critical level yet, but given that the number of people hospitalized for COVID has doubled in three weeks,” Garrow said, “we’re very concerned about our hospitals.”

While early research indicates that omicron may be less likely to send people to the hospital, especially if they are vaccinated and boosted, the speed with which the variant is spreading could still overwhelm providers, even if a smaller percentage of those infected get very sick.

Emergency departments are already taxed, with waits ranging from four to six hours at city hospitals. Should cases continue to rise, hospitals may need to reinstate emergency measures taken during previous surges, including canceling some nonurgent procedures and converting other wards into ICUs.

“We really don’t want to go there like before,” said Rohit Gulati, Einstein Health System’s chief medical officer. “But if it did come to that that’s what we would be forced to do.”

» READ MORE: Pennsylvania and N.J. see COVID-19 cases continue to surge as 2021 ends

Einstein, the most stressed hospital in the city, has about 100 confirmed or suspected COVID-19 inpatients, he said. That’s about a third of the hospital’s total capacity of staffed beds. Overall, the hospital’s medical units are close to 100% capacity, Gulati said.

Doctors noted, though, that this surge is already proving far less deadly than prior ones. Einstein’s ICU now has as many as 10 COVID-19 patients at a time, Gulati said, compared with 50 or 60 a year ago. Hospitals now also have treatments, including antiviral pills from Merck and Pfizer.

“We do have a few more tools and we’ve learned a little bit more from previous experience how to handle it,” Gulati said. “It’s just a matter of what percentage of the population gets sick.”

The latest case surge comes as omicron is spreading more rapidly than previous variants — and evading some vaccine protection — and as more people are getting tested for the virus.

More than 39,000 Philadelphians were tested at city sites from Dec. 20 to 22, heeding the advice of health officials, including Philadelphia Health Commissioner Cheryl Bettigole, who urged testing before seeing family or friends for the holidays. Many others took at-home rapid tests, which are not accounted for in official records.

However, more testing alone does not explain the jump in positive cases. During the seven days ending Dec. 26, more than a quarter of COVID-19 tests done in the city came back positive, compared with 5% the week of Thanksgiving.

Distressing records are being set in the suburbs, as well, with the seven-day average of new cases per 100,000 people reaching pandemic highs in both the Pennsylvania suburbs and South Jersey. The average in South Jersey is the highest, at 110.8 cases per capita.

Hospitalizations have increased 60% in New Jersey over the last two weeks, according to the New York Times, and remained relatively flat in Pennsylvania over the same period. However, Pennsylvania has the third-highest daily average of hospitalized COVID-19 patients in the country.

The rise in cases comes as hospitals are grappling with staffing shortages and are still caring for non-COVID-19 patients.

“We have cases going up. We see the return of influenza,” said John Goldman, a University of Pittsburgh Medical Center infectious disease specialist, “and we’re seeing the return of people to the hospital after delaying care and they end up being sicker than they would.”

In the central and western parts of Pennsylvania, several hospitals were at or near capacity even before Christmas.

Lehigh Valley Health Network was treating 330 COVID-19 patients across its five hospitals Tuesday, a spokesperson said; only 3% of them were fully vaccinated and boosted, none of whom were requiring intensive care.

“We know that there is a solution out there, and it’s just not being utilized,” said Nichole Persing, a nursing director for patient care services who manages a COVID-19 unit at the system’s Cedar Crest campus in Allentown. “It doesn’t have to be like this.”

» READ MORE: Full ICUs, 100 dying a day: The winter coronavirus surge is straining Pa.’s health-care system

Locally, some of the burden on hospitals could be avoided. People who are not experiencing serious COVID-19 symptoms are going to emergency rooms unnecessarily, Gulati said.

“We’re asking most individuals not to come, especially if they have mild symptoms,” he said.

The vaccinated and boosted are especially protected against severe infection, medical experts say. That could help Philadelphia and its collar counties, which are more vaccinated than much of the rest of the state and where a higher percentage of hospital beds remain available than in the commonwealth overall.

“We are not where we were last year,” said Lisa O’Mahony, Delaware County’s medical adviser.

Outside Philadelphia, 59% of all Pennsylvania residents are fully vaccinated with two doses of Pfizer or Moderna or one dose of Johnson & Johnson. Locally, however, about 62% of Philadelphians are completely immunized and about 70% are in each of the collar counties.

About 30% of fully vaccinated Pennsylvanians outside of Philadelphia have received a booster shot, according to state data, as have about 40% of New Jerseyans, Gov. Phil Murphy said last week.

Jennifer Horney, founding director of the University of Delaware’s epidemiology program, said we likely won’t know omicron’s impact on mortality rates until the end of January, but she is optimistic based on preliminary analyses of the variant’s behavior in South Africa.

“While we do have a lot of people in the hospital, vaccinated people are not getting severely ill for the most part with omicron,” Horney said. “If that continues to hold, hopefully our next few weeks won’t look that bad.”

Public health experts emphasize that vaccination is the most effective tool for keeping hospitalizations and deaths at bay.

“Just because we’re seeing a lot of mild cases with omicron doesn’t mean people should not consider getting vaccinated and boosted as soon as they’re eligible,” Horney said.

The nearly 126 million Americans who are unvaccinated are at especially high risk. It would only take severe infections in a small percentage of this population to swamp hospitals, Gulati said.

And as community spread intensifies, people at the highest risk of serious COVID-19 infections, including the elderly and immune-compromised, aren’t guaranteed safety, even with vaccination.

“The cases, the last couple that have come in, they actually had their boosters,” said Kelly, the Einstein nurse. “They have some comorbidities and all that, but it’s still concerning that even with the boosters they’re coming in sick.”