In sum, Maryland added more than 25,000 new coronavirus cases over the holiday weekend. Between Thursday and Sunday, while officials were not updating state statistics, the state’s seven-day average positivity rate jumped from 12.8% to 15.85%.

Nationwide, fears about omicron have reached a fever pitch. Although studies in countries have indicated this variant of the virus is significantly less likely to result in hospitalization, it also spreads much more rapidly, meaning many vulnerable people — particularly the unvaccinated — could become infected, filling hospital emergency rooms and ICUs and endangering even those waiting for care for other ailments.

On Dec. 24, a record 9,859 new cases were added to Maryland’s tally, and 9,350 more came on Dec. 25, Christmas Day. Sunday, state health officials reported 5,826 new cases. The three days reflect more than triple the number of new cases reported over the same time period last year.

A spokesman for Gov. Larry Hogan pointed to large amounts of testing to help explain the surge. Indeed, Dec. 23 set a COVID testing record, with 96,074 tests administered in the previous 24 hours. But on Christmas Eve, the tally sunk to about 65,000 tests, just below the previous record set last December. On Christmas Day, about 33,000 tests were reported, and 24.86% of them came back positive.

“We will continue expanding our testing capacity even further to handle the surge,” spokesman Mike Ricci wrote in an email.

In a statement, Maryland Department of Health spokesman Andy Owen said the “overwhelming majority” of Marylanders hospitalized with the virus have not been fully vaccinated, and advised all residents to get vaccinated and boosted.

“State health officials are urging Marylanders to take this surge seriously,” Owen wrote in an email. “We strongly recommend layered prevention strategies, including wearing masks and practicing social distancing when in the company of others indoors, and getting tested if experiencing symptoms or traveling. If you haven’t yet, it’s important to get vaccinated or boosted as soon as possible.”

As of Sunday, some 1,584 Marylanders were hospitalized with COVID, according to state data, which is 34 more than previously reported. Of those patients, 326 required intensive care. Health officials reported 16 children were hospitalized because of the virus, including four in the ICU. State health experts previously said more than 70% of coronavirus patients were unvaccinated.

The hospitalization rate continues to hold steady above 1,500, which is the state-instituted threshold that triggers hospitals to implement their emergency pandemic plans immediately. That benchmark was initially reached Dec. 23.

Under Gov. Larry Hogan’s directive, Maryland hospitals are to optimize bed capacity and bring in additional staffed beds, redeploy or alter staffing models, reduce non-urgent and elective surgical procedures, transfer patients to alternative care sites and convert spaces used for administrative or other functions to be utilized for clinical care, Hogan’s office said in a news release. The Republican governor himself recently contracted the coronavirus, despite being fully vaccinated and boosted.

“One key number we will be tracking in the coming weeks is our COVID hospitalization levels,” Ricci said Sunday. “As the governor said last week, we are projecting we will exceed our previous highs, and go above 2,000. That’s why we are cautioning Marylanders to not let their guard down, and go out and get their booster shots now.”

Two thousand COVID-19-related hospitalizations at one time would be a record for the state.

At least one state hospital system has gone beyond Hogan’s recommendations. On Friday, Harford County’s University of Maryland Upper Chesapeake Health system declared a hospital disaster, as their numbers of COVID cases skyrocketed. In the past month, the number of COVID-19 positive patients jumped 733% at the system’s Bel Air Hospital and 458% at UM Harford Memorial Hospital in Havre de Grace, the system said.

Marcy Austin, the county’s interim health officer, has been meeting regularly with hospital system officials and the county’s Department of Emergency Services to “stay abreast of the current hospitalization crisis,” health department spokeswoman Ronya Nassar wrote in an email Sunday.

As a result of the current surge, the county health department and emergency services department is working to open COVID testing sites at fire stations in four corners of the county starting in January, Nassar wrote.

The full scope of omicron’s dominance has not yet been fully seen in Maryland, after a cyberattack at the Maryland Department of Health caused a two-week coronavirus data outage.

As a result of the cyberattack, some COVID-19 data for Maryland remains unavailable, including the number of deaths tied to COVID-19 since Dec. 4. Data for the number of cases by jurisdiction or demographic data associated with those cases is also unavailable. Officials have not provided a timeline for when that data will be available again.

In Harford, officials are eager for the county-level data’s return, though they know it’s “safe to assume” they’re seeing high levels of transmission based on the hospitalization tallies locally.

“We are hopeful that the state can update the jurisdictional data soon so that we can return to providing up-to-date information to our residents on our website,” Nassar wrote.

Testing sites across the region have been inundated with long lines, and last week, most places advertising free at-home tests quickly ran out. After taking tests at home, users are asked to report their results via an app, though not all will.

As of Sunday, about 70% of Marylanders have completed their first course of vaccinations either by receiving two doses of the Pfizer/BioNTech or Moderna vaccines or the single-shot inoculation made by Johnson & Johnson, according to the health department. Roughly 1.52 million booster shots have been administered in Maryland.

The steady stream of COVID patients is further straining hospitals, which are treating people with other ailments like the flu and are struggling to grapple with fatigued health care professionals.

And now, both the vaccinated and unvaccinated are getting sick with the rise of the highly transmissible omicron variant. About 40% of Maryland’s cases account for the pandemic’s latest variant. Experts say vaccinations and booster shots are powerful tools to blunt the effects of COVID-19, though they may not prevent illness altogether.

U.S. health officials have said that omicron is the dominant strain of the virus circulating nationally. So far, preliminary results from studies out of the United Kingdom have shown that omicron infections tend to be milder than with previous COVID-19 variants. Those who contract the omicron variant are 15% to 20% less likely to end up in the hospital than those who contracted the delta variant, and they’re 40% to 45% less likely to be hospitalized for a night or more, according to The New York Times.

Some of that reduction may be attributed to the fact that omicron is better at infecting individuals who have previously tested positive for COVID-19, and those individuals are less likely to be hospitalized. But hospitals are expected to continue to be flooded, given that the variant spreads so quickly, experts say.

“We’ve obviously got to do better,” Dr. Anthony Fauci said an interview that aired Sunday on ABC’s “This Week.”

”I think things will improve greatly as we get into January, but that doesn’t help us today and tomorrow,” Fauci said.

Fauci said he was pleased with evidence that omicron causes less severe illness for most people. But he warned against complacency because the rapid spread of the disease could “override a real diminution in severity,” because so many more people could get infected.

There are still many questions about how bad the omicron surge will be in the U.S., Johns Hopkins infectious disease specialist Dr. Amesh Adalja said Sunday.

”There are multiple signals showing decreased severity. But the problem is, we have many high-risk individuals that are not vaccinated in some parts of the country. And there are hospitals in those regions that already are dealing with a lot of delta patients,” Adalja said.

The Associated Press contributed to this report.