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Christmas would have been the first time in a year that Lorenzo Simpson saw extended family members because of pandemic cancellations, but he woke up that day with a sore throat and a sinking feeling. Covid positive for the second time, the 30-year-old isolated in his Hyattsville, Md., home with supplies from CVS instead of holiday helpings.

"I like to eat, so that's a huge low," he said.

The coronavirus, combined with lingering flu, RSV and even Strep A cases, derailed many a holiday celebration this year — with more disappointment to come as new infections lead to missed school and work.

In addition, a new and more contagious variant of the coronavirus is widely circulating in the Northeast, leading to new infections better at evading immunity from vaccinations and previous illness, public health experts say. Schools, which have seen surges in illness after the holidays throughout the pandemic, are aiming to reduce absences with required testing and immunizations.

The variant XBB.1.5 rapidly emerged as the dominant strain in the Northeast in recent weeks, according to modeling data from the Centers of Disease Control and Prevention. In the region that includes Washington, D.C., Maryland and Virginia, the variant makes up nearly half of new infections, followed by BQ variants.

"This is what happens when a variant gets displaced. A variant is not going to displaced by a variant that moves more slowly," said Neil J. Sehgal, an assistant professor of health policy and management at the University of Maryland School of Public Health.

As with previous strains, monoclonal antibodies are ineffective against XBB, but Sehgal stressed that the bivalent booster, updated in the fall, still offers some protection against the new variant.

"All signs right now point to significant cross-protection from the bivalent booster," he said. "Not perfect but still quite good and certainly better than not being boosted at all . . . Yet we've still seen pitifully low uptake of the bivalent booster."

While about 37 percent of people over 65 have gotten the updated booster nationwide, that number shrinks to about 17 percent for people 18 and older, CDC data show.

Although reluctant to predict the behavior of an unpredictable virus, public health experts expect to see an increase in coronavirus infections and more hospitalizations after the holidays, as has happened consistently over the past three years.

Everyone seems to know someone who is sick at the moment. Simpson said he was disappointed to miss celebrating the Yuletide with his mother and extended family, including a brother who traveled from Rochester, N.Y., but he couldn't ignore his runny nose and telltale loss of taste and smell signaling a coronavirus infection.

Nearly a week later, he still felt woozy but was reluctant to miss a shift at the restaurant where he works as a server — a lucrative gig during the holidays. Simpson's boss will allow him to return to work since he has isolated for five days, the period of time in which the CDC says people are most infectious after a positive test result.

Pediatricians are seeing a decline in flu, covid and RSV among school-aged children, but Gabrina Dixon, a pediatric hospitalist at Children's National Hospital in Washington, D.C., said she anticipates a resurgence after the holiday break.

"When kids go back to school and they start commingling, we are concerned that we will see an increase in the numbers again," Dixon said. "The most important thing is [preventive] care."

Dixon encourages parents to make sure they have had flu and coronavirus vaccinations to lessen the severity of illness. She said parents and schools should also stress the importance of hand washing and using hand sanitizer to prevent the spread of germs. Wearing high-quality masks, she said, would also protect children from contracting viruses as they return to school.

Rising illness rates are leading two school systems in New Jersey — Paterson Public Schools and Camden City School District — to require mask after the winter break, and Philadelphia schools will also require masks for the first 10 days when classes resume in January.

Boston Public Schools is also requiring masking for eight days after winter break. Masking is optional in school systems in the Washington, D.C., area, but with much of the metro area in a "medium" covid community level, as determined by the CDC, Maryland's Montgomery County Schools encouraged masking indoors.

"After prior holiday breaks, we have seen the highest transmission risk for respiratory infections in the 2 weeks after students return to school," the school system's medical officer said in a message to families before the break.

Montgomery County schools sent home coronavirus test kits with staff and students and recommended testing before returning to school.

Washington, D.C., schools also provided test kits and will require students and staff to submit proof of a negative coronavirus test before they return to class. The school system's "test-to-return" requirement has been in place throughout the pandemic at the beginning of the school year and after holiday and other breaks.

City officials have said the required testing is necessary to safely reopen schools and maintain in-person learning.

But Dixon noted there is no screening for the flu or RSV and even some symptomatic children test negative for covid, hence this blanket recommendation: "If you are sick, don't go to school."

At-home testing and much less frequent data reporting mean secondary markers such as work and school absences will define the next surge, Sehgal said. The Virginia Department of Health began updating covid data less frequently as of this week and moved data on outbreaks and other metrics off the main dashboard; the agency stopped recommending widespread masking long ago.

Maryland's Montgomery County on Friday urged residents to "play it safe traveling over the holidays" and to wear masks, tweeting "spread love not germs" and the hashtag #MaskUpMoCo.

Although masking has fallen by the wayside on public transportation and elsewhere, Sehgal said the simple act of wearing a mask can curb the spread of the coronavirus as well as other illnesses wreaking havoc on families.

"There's been this collective forgetting about how we protect ourselves and each other," he said, calling the move away from masks a "self-inflicted wound."

William Petri, a professor of infectious diseases at the University of Virginia School of Medicine, said that given the decline in RSV cases, without a vaccine, the region could be seeing the end of the worst of the respiratory illness season.

Or, he said, "maybe it's the eye of the storm."

The Washington Post's Lauren Lumpkin contributed to this report.