• "It's hard to process what's actually happening right now, which is most people are going to get Covid," acting FDA Commissioner Janet Woodcock said.
• She said the U.S. must ensure essential services are not disrupted by the record levels of new infections.

Acting Food and Drug Administration Commissioner Dr. Janet Woodcock gave U.S. lawmakers an ominous warning this week: The nation needs to ensure police, hospital and transportation services don't break down as the unprecedented wave of omicron infections across the country forces people to call out sick.

"It's hard to process what's actually happening right now, which is most people are going to get Covid," Woodcock testified before the Senate health committee on Tuesday. "What we need to do is make sure the hospitals can still function, transportation, other essential services are not disrupted while this happens."

Much like last winter when public officials were trying to contain the spread of Covid, public services and businesses across the U.S. are cutting back and limiting hours, some even temporarily shutting down. This year, however, so many workers are out sick with the virus, it's disrupting services that public officials are otherwise trying to keep open.

From New York to Los Angeles, emergency services are struggling to staff enough police, nurses, EMTs and firefighters as more and more workers call out with Covid. Public transit systems in New York and Chicago are suspending or have disrupted some services, airlines are cutting back flights, and public officials have been forced to quarantine at home as the highly contagious omicron variant pierces through vaccine protection and sends large swaths of mostly unvaccinated people to the hospital.

The U.S. reported a pandemic record of almost 1.5 million new Covid infections on Monday with an average of about 750,000 new infections every day over the last week, according to CNBC analysis of data compiled by Johns Hopkins University. That compares with a seven-day average of about 252,000 new cases a day a year ago.

Hospitalizations are also higher than last winter's peak — before the widespread distribution of vaccines — and continue to rise. More than 152,000 people in the U.S. were hospitalized with Covid as of Wednesday, up 18% over the last week, according to data tracked by the Department of Health and Human Services.

"Many places across the country are getting to the point where even their backup staff are getting sick," Dr. Gillian Schmitz, president of the American College of Emergency Physicians, said in an interview. She said the strain on front-line workers is worse now than at any other point in the pandemic. "Pretty much the whole country right now is feeling this surge of cases that is impacting staffing."

Hospitals faced a shortage of nurses well before the U.S. first detected a case of the omicron variant in early December. The American Nurses Association in September called on the Biden administration to declare the nursing shortage a national crisis, as the delta variant was surging in many parts of the country at that time.

"The nation's health care delivery systems are overwhelmed, and nurses are tired and frustrated as this persistent pandemic rages on with no end in sight," ANA President Ernest Grant said at the time. "Nurses alone cannot solve this longstanding issue and it is not our burden to carry," Grant said.

The omicron variant now threatens to compound the long-standing staff shortages at hospitals by forcing nurses to call out sick. Although most nurses are fully vaccinated, omicron is able to evade some of the protection provided by the shots, causing more and more breakthrough infections around the country.

An average of more than 1,000 hospitals nationwide are currently reporting daily critical staffing shortages, according to HHS data. However, it's likely an undercount because many hospitals were not reporting their status as of Wednesday

"The sudden and steep rise in cases due to omicron is resulting in unprecedented daily case counts, sickness, absenteeism and strains on our health-care system," CDC Director Dr. Rochelle Walensky told reporters at a White House Covid-19 news briefing Wednesday. To help ease potential staffing shortages, the agency last month slashed the isolation time for some health-care workers who get Covid — a controversial move that's come under fire by nursing groups across the country.

Dr. Gabe Kelen at the Johns Hopkins Hospital said there have been days where several hundred employees have called out sick across the system's five hospitals in Maryland and Washington, D.C. Kelen said that includes everyone from nurses to facilities staff who clean patient rooms, prepare food and stock rooms.

"You can just see how astoundingly hampered the operations are at a time when institutions like ours need to ramp up staffing," said Kelen, who chairs the department of emergency medicine at Hopkins and directs its preparedness and response office.

"Given how crushed health-care services are right now, to lose nurses for even a five-day period should they have had a mild infection is just a tremendous, tremendous loss," Kelen said.

The Biden administration has deployed hundreds of military doctors and nurses to support overwhelmed hospitals and directed the Federal Emergency Management Agency to provide emergency hospital beds and deploy ambulances and EMS crews to transport patients.

Police, fire and transit agencies are also struggling with staffing as omicron forces people to call out sick. In Los Angeles, Mayor Eric Garcetti said more than 800 police and firefighters were isolating at home due to positive Covid test results as of last Thursday.

"This is an incredibly tough moment. The omicron variant has taken off like wildfire," Garcetti said during a news conference.

In New York City, 18% of EMS staff and 13% of firefighters are out sick with Covid as of Tuesday, down from 30% for EMS and 18% for firefighters a few days prior, according to the FDNY. The New York City Police Department told CNBC on Tuesday that 12.5% of the force was out sick as of last Friday.

New York's subway system, the nation's largest, has also suspended service on some lines due to staff shortages caused by omicron. The Chicago Transit Authority, which operates the nation's second-largest public transit system, has also told the public there may be service disruptions as workers are calling out sick due to Covid.

The virus is also infecting top city and state officials. Chicago Mayor Lori Lightfoot said Tuesday she tested positive for Covid and will work from home while she isolates with cold-like symptoms. Lightfoot said she was fully vaccinated and boosted. West Virginia Gov. Jim Justice announced early Wednesday that he also tested positive, despite also being fully vaccinated and boosted.

Airlines began canceling flights just before Christmas because omicron infections among staff left them short-handed. United, JetBlue Airways, Alaska Airlines, SkyWest and others have trimmed January schedules as Covid cases surge, leaving them without the pilots and other employees they need.

United's CEO on Monday told staff that 3,000 workers, about 4% of its U.S. workforce, were positive for Covid.

"Just as an example, in one day alone at Newark [New Jersey], nearly one-third of our workforce called out sick," Scott Kirby said in a staff note.

White House chief medical advisor Dr. Anthony Fauci told the Senate health committee on Tuesday it's unclear when the omicron wave will peak due to variation in vaccination coverage across the U.S. Fauci said omicron infections may rise in some parts of the country while they peak and fall in others.

"It is a very wily virus," Fauci told lawmakers at the hearing. "It has fooled everybody all the time — from the time it first came in to delta to now omicron — it's very unpredictable and we're doing the best we possibly can."

 — CNBC's Leslie Josephs and Nate Rattner contributed to this report