Californians are once again required to mask up indoors starting Wednesday as the state contends with climbing coronavirus case numbers and concerns about the worrisome new omicron coronavirus variant.

The state is mandating that masks be worn in all indoor public settings — regardless of COVID-19 vaccination status — for the next four weeks, through Jan. 15, 2022.

While several counties have imposed their own mask mandates after California’s “grand reopening” on June 15, about half of the state’s population has lived in counties that do not have mask requirements.

Residents in Los Angeles County have gotten used to masking up indoors thanks to a county-enacted mandate. But others in counties like Orange and San Bernardino haven’t been required to wear masks indoors since the state dropped its previous mask mandate in the summer.

Where are masks required?

Face coverings are now required for everyone in all indoor public settings like gyms, malls, restaurants and stores.

Masking was already required for unvaccinated workers at high-risk congregate and other health care settings.

Why is California bringing back masks?

State officials said masks will bring an added layer of protection as the omicron variant is increasingly being found across California.

The new measure also comes during the holiday season, when families are more likely to travel and gather in larger numbers.

And while officials had removed the previous mask mandate amid optimism over how the availability of vaccines will limit the spread of the virus, there remains pockets in the state with low vaccine coverage.

California has also seen an uptick in coronavirus case and hospitalization numbers in recent weeks.

Since Thanksgiving, the state’s seven-day average coronavirus case rate has climbed by 47% and hospitalizations have increased by 14%, according to the California Department of Public Health.

While current numbers are still lower than during last year’s winter COVID-19 surge, the current increases come as around 70% of Californians have received at least one vaccine dose.

Los Angeles County’s health director last week announced the county could already be seeing the beginning of another COVID-19 winter surge.

The worry now is about the state’s hospital capacity as the state struggles with staff shortages, Health and Human Services Secretary Dr. Mark Ghaly said in a briefing Monday.

Officials say even a moderate surge in cases and hospitalizations could impact California’s health care delivery system.

“Frankly, hospital capacity is still pressed and challenged,” Ghaly said. “We see that in parts of Southern California, Riverside, San Bernardino, Mono, Inyo county, we see it around in and around the Central Valley and San Joaquin Valley, and in the northernmost parts of our state.”

In announcing the new mask mandate, California officials pointed to 10 studies that have confirmed the benefit of universal masking, finding that following directives for universal masking, new infections fell significantly.

“Even a 10% increase in indoor masking can reduce case transmission significantly,” Ghaly said.

California’s mask mandate has the support of the nation’s top infectious disease expert.

“I agree completely with California’s decision on the mask mandate,” Dr. Anthony Fauci told KTLA.

How will it be enforced?

State officials have not provided specifics on how the new mask mandate will be enforced, but Ghaly said the state is expecting most residents to choose to mask up.

“We know that there’s going to be people who don’t necessarily agree with this, who are tired, who aren’t going to mask and we hope that those are few and far between,” Ghaly said.

“We are at a point in this pandemic where we are expecting Californians to heed the warning, understand what we’re seeing or concerned about, and make the choice to mask up for the period of time,” he added.

Are there exemptions?

As with the previous mask mandate, there are people who are exempt from wearing masks at all times.

The exemptions include:

• Those younger than two years old. (Young children aren’t included because of the risk of suffocation.)
• People with medical or mental health condition, or disabilities, that prevent them from wearing a mask. (This includes those who are unconscious, can’t remove a mask on their own or who have a medical condition that will mean wearing a mask could obstruct their breathing.)
• People who are hearing impaired, or communicating with someone who is hearing impaired.
• People who can’t wear a mask because it would create a risk to them related to their work — as determined by workplace safety guidelines.

Also, California is exempting San Francisco from the new mask mandate.

Fully vaccinated people in San Francisco will be able to remove their masks in gyms and workplaces.

That’s because about 86% of the city’s eligible residents have received at least one COVID-19 vaccine shot, according to San Francisco’s public health department.

“It’s a recognition of all of the thought and care that San Francisco residents have been putting into staying as safe as possible,” San Francisco’s health officer Dr. Susan Philip said of the state’s decision.