A new coronavirus strain is gaining a foothold in the region and country, and combined with other common winter viruses it’s making for another tough stretch in Maryland hospitals.

Experts predicted an uptick in COVID-19 cases after the holiday season, particularly because fewer people have been wearing masks, distancing or getting booster shots to replace a decline in immunity. The new subvariant, XBB.1.5, is piling on. The World Health Organization says it’s the most transmissible form yet.

“It does seem to be spreading fast,” said Matthew Frieman, a longtime coronavirus researcher and an associate professor of microbiology and immunology at the University of Maryland School of Medicine.

“With waning immunity, there are more chances of being infected.”

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The number of cases is unknown because most people recover at home and don’t report their positive rapid tests, leaving hospitalizations and deaths as measures of the rising infections.

There were 833 people hospitalized in Maryland with COVID-19 Tuesday, up 31 people from a day earlier, and 27 deaths. While the total hospitalized is less than a quarter of the total at the pandemic peak a year ago, the number is the highest since February.

The good news is that most everyone has had multiple shots of vaccine, infections or both, and the body can still mount a defense, said Dr. Greg Schrank, an epidemiologist and infectious disease physician at the University of Maryland Medical Center.

That means many people aren’t getting severe cases, he said.

More people in the hospital now, compared with a year ago, are “with COVID-19″ and not “for COVID-19,” he said. That means they came for another reason and tested positive. Some have other viruses, others have something unrelated to a viral infection. Last year, more people were coming in and their chief complaint was, “I can’t breathe,” Schrank said.

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“That said, in the past few weeks, we have seen more cases of COVID respiratory infections that are quite severe,” he said.

Most hospitalized people are elderly or immunocompromised, and can’t mount the same defense as younger, healthier people.

Schrank and Frieman both said younger, healthier people still should not be cavalier about becoming infected with COVID, or any virus. Anyone can still become really sick, and it’s no fun to miss school or work for a week on the sofa feeling awful.

There also is the risk of long COVID, which is a poorly understood condition where people even with mild cases continue to have symptoms or get new symptoms that linger.

Plus, it’s important to protect friends, family and neighbors from the virus — and other viruses that are circulating, they said.

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Those hospitalized with COVID (833) are outpacing the number now hospitalized with other respiratory viruses, including RSV (20) and influenza (94), which had swamped hospitals but peaked weeks ago, state data shows.

The Maryland Hospital Association reports that most hospitals are more than 90% full and many are at capacity, contributing to longer wait times for all patients. Officials are asking the public to avoid the emergency rooms if people have less serious medical needs and can visit a doctor’s office or urgent care center.

Bob Atlas, president and CEO of the association, said people should wear masks that cover their mouths and noses when they are around larger groups and keep their distance if possible.

He said they should also get tested for COVID-19 if they have symptoms or someone close to them has tested positive.

He also said people should stay home if they are sick and get vaccinated against COVID-19 and the flu.

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“Likely as a result of holiday gatherings, hospitals are seeing generally sicker patients coming into the emergency departments due to a number of illnesses, including the new COVID-19 variant XBB.1.5, the flu, and others,” Atlas said. “Hospitals are still facing staffing shortages and that, combined with increased demands on the emergency departments and other hospital resources, are the biggest concerns.”

More than 90% of Marylanders have gotten vaccinated against COVID-19, according to state health data. But only about a quarter of those fully inoculated have gotten the bivalent booster that offers protection against severe illness from the original virus and from omicron variants. Officials say the booster offers protection against XBB.1.5.

After emerging last month, the subvariant is responsible for about 32% of cases in the region that includes Maryland, according to the U.S. Centers for Disease Control and Prevention. That’s higher than the national proportion of about 27%.

Frieman said there are new treatments and vaccines in the works, and it’s possible that people will eventually have the option of an annual COVID vaccine, like the one to protect people from the flu.

“We’re only in year three of this virus and learning what the virus can do,” he said.

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“We should be able to design a vaccine with broad protections that last longer,” Frieman said. “Maybe that will mean more people will be interested in getting it.”