And though some nontraditional manufacturers like T-shirt factories and other apparel makers have announced plans to rush-produce masks, it’s unclear that they will be able to meet required safety standards or shift over production in time to answer demand.

Few in the protective equipment industry are surprised by the shortages, because they’ve been predicted for years. In 2005, the George W. Bush administration called for the coordination of domestic production and stockpiling of protective gear in preparation for pandemic influenza. In 2006, Congress approved funds to add protective gear to a national strategic stockpile — among other things, the stockpile collected 52 million surgical face masks and 104 million N95 respirator masks.

But about 100 million masks in the stockpile were deployed in 2009 in the fight against the H1N1 flu pandemic, and the government never bothered to replace them. This month, Alex Azar, secretary of health and human services, testified that there are only about 40 million masks in the stockpile — around 1 percent of the projected national need.

As the coronavirus began to spread in China early this year, a global shortage of protective equipment began to look inevitable. But by then it was too late for the American government to do much about the problem. Two decades ago, most hospital protective gear was made domestically. But like much of the rest of the apparel and consumer products business, face mask manufacturing has since shifted nearly entirely overseas. “China is a producer of 80 percent of masks worldwide,” Laverdure said.

Hospitals began to run out of masks for the same reason that supermarkets ran out of toilet paper — because their “just-in-time” supply chains, which call for holding as little inventory as possible to meet demand, are built to optimize efficiency, not resiliency.

“You’re talking about a commodity item,” said Michael J. Alkire, president of Premier, a company that purchases medical supplies for hospitals and health systems. In the supply chain, he said, “by definition, there’s not going to be a lot of redundancy, because everyone wants the low cost.”

In January, the brittle supply chain began to crack under pressure. To deal with its own outbreak, China began to restrict exports of protective equipment. Then other countries did as well — Taiwan, Germany, France and India took steps to stop exports of medical equipment. That left American hospitals to seek more and more masks from fewer and fewer producers.