As the highly contagious omicron variant explosively spreads and fills hospital beds across the region, health experts are urging Southern Californians to switch from cloth face coverings to more robust, tightly fitting masks that better protect them — and others — from the coronavirus.

“You have to mask better than before,” said epidemiologist Andrew Noymer, an associate professor of population health and disease prevention at UC Irvine.

“In the face of the highly transmissible omicron, the cloth masks are pure theater,” Noymer said. “They don’t do anything.”

The push to upgrade face coverings comes after California officials extended the statewide indoor mask mandate that went into effect in mid-December for another month, until  Feb. 15.

In some cases, officials are making the switch to better masks a requirement.

• Los Angeles County recently mandated that K-12 teachers in the county wear higher-grade masks.
• USC students and professors must upgrade masks they wear on campus starting Tuesday, Jan. 18, according to a notice sent Wednesday, Jan. 5, by university officials.
• Also on Wednesday, the LA County Department of Public Health ordered employers whose employees work indoors, in close contact with people, to provide tight-fitting medical-grade masks, surgical masks or respirators such as the N95 and KN95 for them by Monday, Jan. 17.
• As K-12 schools in the nation’s second-largest school district, Los Angeles Unified, prepare to return to campus Tuesday, Jan. 11, masks will be required at all times. That’s outdoors as well as indoors. All district employees must wear surgical masks, or those of higher quality. LA Unified kids don’t face a mandate on mask type, but educators recommend that “all students wear well-fitting, non-cloth masks with a nose wire. “
• Chapman University announced Friday, Jan. 7, it is requiring everyone who goes on campus to wear a surgical mask or a higher-quality model, as in-person instruction returns Monday, Jan. 10. The university said it will make available disposable medical grade surgical masks and KN95 masks. The decision follows a petition signed by more than 300 students calling on the Orange County university to distribute free KN95 masks.

Senior Daniel McGreevy, who founded Chapman Mask Project and started the petition, said that “while we want to remain on campus, we want to do so safely, and the science is clear that better masks like KN95s will prevent the spread of COVID in a way that most other masks won’t.”

What’s driving the call for more effective face coverings is the unprecedented surge in infections against the backdrop of increasing evidence that the coronavirus forms tiny aerosols that float in the air, said Dr. Russell Buhr, a pulmonary and critical care doctor at UCLA Health.

“Aerosols can stay suspended in the air so much longer because they are lighter and smaller,” Buhr said.

And, Noymer said, the tiny particles squeeze “between the threads of a cloth mask.”

Higher-grade masks are better equipped, experts say, to block potentially infecting particles and should be used from this point on — even after the omicron wave begins to subside. Noymer said people should wear better masks “until further notice.”

To help people choose a covering that provides adequate protection, the California Department of Public Health offers this assessment of masks’ ability to ward off COVID-19:

• Most effective: N95
• More effective: KF94, KN95, double mask, fitted surgical mask
• Effective: Surgical mask
• Least effective: Fabric mask with three or more cloth layers

Angel Acevedo, who lives in Yucaipa and works in a Moreno Valley office, said he and his family had been wearing surgical masks.

Then over the holidays, Acevedo learned he had been exposed at work. He wanted better protection and peace of mind, so he ordered four boxes of N95 masks online, just before the end of the year.

Acevedo said he did so to protect his family — especially his mother, who lives with him, is just shy of 70 years old and has underlying health conditions.

“Now I don’t walk out of the house without having an N95,” he said. “We’re in the midst of the highest level of spread that we have ever been in, which I think warrants the extreme measure of the N95.”

Dr. Anissa Davis, the Long Beach city health officer, said people at high risk of becoming severely ill from COVID-19 or who live with people who are should choose a high-grade mask.

No matter what mask a person buys, though, it is crucial that the covering be worn properly — over the mouth and nose, Davis said. She often sees masks covering people’s mouths, but not their noses.

“Sometimes they have it hanging off their chin,” she said.

Dr. Jennifer Chevinsky, Riverside County’s deputy public health officer, said it’s also important that a mask fit a person’s face snugly and “not have gaps around the sides.” The goal, she said, is to have the air people breathe and exhale go through the mask, not around it.

In short, Chevinsky said, “It all comes down to fit and filtration.”

The better a mask fits one’s face and filters the air, the more protection it provides, she said.

Buhr, the UCLA doctor, said there is a way to check if a mask is filtering the air you breathe. When breathing in, he said, you should notice the mask “shrink down on your face a little bit,” or pull towards the face.

“That tells you that the air is coming through the mask instead of around the edges,” Buhr said.

There was a time when health officials recommended against buying top-of-the-line masks.

Early in the pandemic, for example, Orange County officials recommended people leave N95 and surgical masks for healthcare workers and use a cloth mask, scarf or bandana instead.

Now, Buhr said, it is a good idea to purchase N95s or similar respirators because the healthcare industry has adequate supplies.

The advice has come full circle during the long pandemic.

For example, USC officials, in their directive to USC students and faculty, said bandanas, neck gaiters, scarves and cloth masks aren’t acceptable. Cloth masks are permitted only if worn in combination with a medical mask beneath — an option that experts say will provide protection.

The shift in masking advice comes as the number of confirmed coronavirus patients in hospitals continues to soar. Hospitalizations reached 779 in Orange County, 791 in Riverside County, 862 in San Bernardino County and 2,902 in Los Angeles County on Thursday, Jan. 6, according to state data. While not as high as patient counts this time last year, at the worst point of the pandemic, more people with COVID-19 are being treated than were during the summer delta surge.

On Friday, L.A. County reported yet another one-day record of more than 43,000 new coronavirus infections, smashing a previous record set the day before, county health officials said.

Making matters worse, Buhr said, the omicron surge is occurring at a time when hospitals are treating many people with other types of respiratory viruses and ailments.

“The hospitals are all really struggling,” said Dr. Troy Pennington, emergency room doctor and emergency medical services physician at the San Bernardino County-run Arrowhead Regional Medical Center in Colton. “The hospitals are filling up and they are running out of available space.”

Omicron, three or four times more contagious than delta, is driving the winter surge, experts say. At the same time, the new variant is believed to be produce generally milder episodes of COVID-19. While some take comfort from that, Buhr warns omicron is “not mild for everyone.”

“People still do die from omicron,” he said.