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As an ICU nurse, Megan Jansen knows the surge of coronavirus patients is coming.

“It seems to me that it’s like the eerie calm before the storm,” Jansen said after a shift this week in the intensive care unit at Salt Lake Regional Medical Center, where she has worked for 10 years.

And though she praises the “fantastic” team planning the hospital’s coronavirus response, Jansen is concerned that hospitals in Utah and nationwide are dealing with shortages in medical-grade supplies — such as the N95 respirators that can filter out the virus.

“It made me so sad for my coworkers, and for the health care world, knowing that we would be going through this with so few supplies,” Jansen said.

On March 20, Jansen woke up with an idea: Starting a Facebook page to gather volunteers to make homemade surgical masks. The masks wouldn’t be a substitute for the N95 masks — but they could be worn over an N95, to catch splashes of liquid and prolong the life of the medical-grade equipment.

The response was immediate. “Within hours, we had hundreds of seamstresses. Within days, we had thousands,” said Jansen, who admits that she cannot sew a stitch. “I had no idea what I was opening myself up to."

Jansen’s Facebook group spawned a website, Sewing for Lives — through which more than 10,000 volunteers nationwide have made, or are in the process of making, some 39,000 masks.

Her effort is just one of many instances in recent weeks of a huge mask-making drive, guided by a shared impulse to help out during the crisis.

Employees at Lehi-based Young Living Essential Oils churned out 2,000 fabric masks for workers at its Spanish Fork warehouse, the company announced Friday. Nationally, fashion designer Christian Siriano put his sewing team to work making thousands of masks for New York health care workers. Fanatics, a company that makes Major League Baseball-licensed apparel, retooled its assembly line to make masks and gowns from jersey fabric — some with pinstripes.

The interest in making masks comes as government leaders and health experts at the state and federal levels wrestle with the question of whether everybody — infected or not, in a hospital or on the street — should be wearing a mask.

On Friday, the White House said the Centers for Disease Control and Prevention has issued a new recommendation that people cover their faces — with a mask, or a scarf or bandanna — when going outside. President Donald Trump, at his afternoon briefing, called the advice “voluntary.”

“I don’t think I’m going to be doing it,” Trump said.

The World Health Organization advises on its website that only people who are coughing and sneezing, or caring for someone who is suspected to be infected with the coronavirus, need to wear a mask.

The Utah Department of Health is waiting for federal guidance about what materials might work best in homemade masks, state epidemiologist Angela Dunn said Friday in a news briefing.

UDOH is anticipating a shortage of surgical masks and N95 masks for professionals as the coronavirus pandemic peaks in Utah, Dunn said. The state is “working with our federal partners and following their guidelines in terms of … recommendations for specific materials that would be best for people to make homemade masks,” she said.

Two of Utah’s biggest hospital chains, Intermountain Healthcare and University of Utah Health, stirred up controversy among volunteer mask-makers last week, when they asked people, politely, not to donate homemade masks to their facilities.

“Homemade cloth masks do not provide the appropriate level of antimicrobial protection for caregivers in close contact with patients with COVID-19,” the hospital groups said in a joint statement.

Intermountain and U. Health pointed to a 2013 study that found homemade masks “would be better than no protection.” They should only be used, the study said, “as a last resort to prevent droplet transmission from infected individuals.”

“If you had one on, it would be like covering your mouth when you cough,” said Cherie Frame, Intermountain’s director of infection prevention. “It is better than nothing.”

The question behind whether masks are effective or not comes down to how the novel coronavirus is transmitted — an issue about which scientists aren’t completely sure.

Most viruses are spread in one of two ways: droplets of liquid, like those expelled when someone sneezes or coughs; and aerosol, even smaller droplets that hang in the air.

A regular one-use paper surgical mask — the kind TV doctors wear on shows like “Grey’s Anatomy” — catches the larger droplets, both those expelled by the wearer or breathed toward the mask from the outside, Frame said.

Those masks don’t catch the smaller aerosol droplets, Frame said. For that, health care workers need a medical-grade mask, like the N95. They have filters that can catch droplets as small as 0.3 microns. (For comparison, a human red blood cell is about 5 microns across.)

In normal conditions, the N95 masks are used once and discarded — but with the N95 masks in short supply, “in an emergency, we use them for as long as we can,” said Jansen, the ICU nurse who founded Sewing for Lives.

Frame said hospitals worldwide have been experimenting with ways to recycle or reprocess N95 masks. One treatment, using ultraviolet light and hydrogen peroxide vapor, has shown promise in studies, she said.

Cotton masks — like those usually made at home — are 50% as effective as paper surgical masks at filtering droplets, Frame said. “It will stop some droplets, but not all of them,” she said.

Some have argued that wearing a mask in public serves as a walking reminder for people to not touch their faces. That’s true to an extent, Frame said, but people wearing masks still touch their faces — and they’re touching a mask that may be holding more microbes than an uncovered face.

“You think you’re being safe, but in reality, you’ve contaminated your hands more,” Frame said.

Also, once a cotton mask gets moist, Frame said, it can become a breeding ground for bacteria. “So remove it and get a different one,” she said.

In the end, Frame said, “wearing a mask safely is important, but even more important is continuing to wash your hands.”

For Jansen, the Sewing for Lives project has been about giving “an additional layer of protection” for anyone who needs it — including long-term care facilities, peace officers and first responders.

It’s also created a community, she said, of “people making the best out of this absolutely horrible situation.”

Jansen cited one woman who had to cancel her daughter’s wedding because of the coronavirus outbreak, and wanted to fill the free time she wasn’t spending on wedding preparations. That woman, Jansen said, made “bride” and “groom” masks for her daughter and future son-in-law, souvenirs for the couple’s rescheduled nuptials.

“It makes you feel like you have a whole group of people with you,” Jansen said. “We’re a 10,000-member family who will probably never meet each other.”