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Welcome to the worst-case scenario.

For weeks, hospitals across the country have warned that life-saving medical supplies are in dangerously short supply amid the coronavirus pandemic. And for many health-care workers, the countdown to that moment is no longer a matter of weeks or days — but hours.

The Post reached out to several local hospitals regarding the need for makeshift face masks, only to find that many physicians are now too inundated caring for patients to speak with the press. But friends and family of hospital staffers have taken to social media to voice concerns on their behalf.

“My sister is a doctor in New York and will be one of the primary doctors taking care of patients with COVID-19,” wrote Kristin Warltier Austin, from Pelham, NY, on Facebook last week. “She has been in touch with doctor friends in Seattle and NYC who are already experiencing a shortage of masks. She asked me to sew her some masks to have on hand as she knows they will be in short supply in the coming weeks. This could be the only protection for our doctors and nurses on the frontline of this war!”

Her sister’s plea inspired Austin and her 12-year-old daughter, Skyler, to begin their own mask-making operation, which has already produced roughly 60 masks.

Skyler tells The Post that she was inspired to help when she learned that “people were hoarding masks and the doctors were left with nothing.”

“I wanted to do something to help my auntie and the other doctors who are risking their lives for us,” says the seventh-grader.

“They all sounded terrified,” says Kristin of her sister and her hospital colleagues. “The masks are what seemed the most in need, so I went to YouTube, found a video and got out my sewing machine.” She then asked the community groups Junior League of Pelham and Pelham Together as well as the Moms of Pelham Facebook group to join their effort.

The pair now has over 50 volunteers pledging to donate materials and craft homemade masks. They also coined the hashtag #sewmaskssavelives, which, as they hoped, is catching on.

After seeing the Austins’ call to action on Facebook, Virginia-based children’s clothing company Daddy’s Little Dress Shirts made a similar plea to their Facebook followers.

“News are telling us that some hospitals are running low on face mask. They are calling on us that know how to sew and have sewing machines at home to help reach the #100million face mask,” wrote business owner Maria Mandaro. “If you know how to sew and have a machine at home I be adding the information in our story’s today. Let’s all help and make some of this mask. Our hospitals are in need and we can make a difference.”

Austin and Mandaro’s micro-operations are just two among many taking to social media to ask for more volunteers. Even major retail brands and designers are putting a hold on fashion to produce masks, including Nashville, Tenn., designer Elizabeth Suzann and New York-based designers Rachel Comey, Christian Siriano and Estrada Twins.

“Although the masks are not medical grade, as fashion designers, we felt like it was our duty to give back and provide a barrier that is much needed to prevent the spread of any virus for the safety of all essential workers,” Antonio Estrada, who owns the business with his twin brother Jesus, a contestant on Season 7 of “Project Runway,” tells The Post.

Despite these heartwarming efforts, many in the medical field are sharing their concerns over the prospect of relying on cloth masks in the clinical setting — and urging medical supply manufacturers to ramp up production of personal protective equipment (PPE) using the hashtag #GetMePPE.

Many also point out that the US has fallen short from the get-go. An alarming photo shared on Twitter last week shows hospital workers in China and Italy in head-to-toe protective suits and face shields; meanwhile, those in the US are fashioned with just loose-fitting gowns, gloves and paper masks, leaving many areas of the body exposed.

While surprisingly few studies have been conducted to show the efficacy of face masks –– particularly those made of household materials –– the ones that do exist, such as a 2013 study by Cambridge University, caution that these makeshift masks “should only be considered as a last resort.” Researchers found that, on average, cloth masks fit only half as well as surgical masks — which means bacterial and viral aerosols have a greater shot of escaping or entering the mask area. Commercial masks were found to be “three times more effective in blocking transmission [of particles]” compared to homemade masks.

A randomized clinical trial from 2015 revealed similar results. The report, published in BMJ Open, concluded that “moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection.” Researchers added that “cloth masks should not be recommended for [health-care workers]” particularly in “high-risk settings.”

And what could be more high-risk than a global pandemic?