Public health officials are warning that a massive ramp-up in the number of tests for the coronavirus coupled with disruptions to the global supply chain are creating new shortages of some of the chemicals needed to process those tests.

The result could be a catastrophe that would grind progress fighting the virus to a halt.

The chemicals, known as reagents, are used in different elements of different tests. They are substances or compounds added to a bodily sample, like a nasal or throat swab. If the virus is present, the reagent will create a chemical reaction that a diagnostic machine can detect.

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Different tests use different chemicals to elicit those reactions, but no matter which chemicals they use, without reagents tests cannot be processed.

If the states and cities that are so rapidly increasing their capacity to test for the coronavirus run out of the reagents they need, the testing process would come to a complete halt.

“It's like the water you add to your coffee pot. The test is the grounds, but the water you add in is what makes it all work. So if you don't have these reagents, you can’t make the test work,” said Michael Osterholm, who directs the Center for Infectious Disease Research and Policy at the University of Minnesota. “Every test uses reagents, some kind or another. They're not all the same.”

Several major laboratory corporations that are processing thousands of coronavirus tests every day have privately signaled they are running low on supplies. The Centers for Disease Control and Prevention (CDC) said it too is keeping a close eye on global reagent supplies, and on the supply chains that have been disrupted both in China and around the world.

“Many of the commercial tests that are now out there in use through emergency use authorizations that have basically come online rely on components that are in limited supply,” Anne Schuchat, the CDC's principal deputy director, said in an interview. “The global supply for many things is limited, and for the reagents, for the different molecular tests, the diagnostic tests, that’s a challenge.”

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Schuchat said the strain on supply has come as the number of tests conducted on the potentially sick rises throughout the United States. Laboratories around the country are testing about 100,000 people a day, according to data collected by the COVID Tracking Project, a huge ramp-up for tests that did not exist just weeks or months ago.

“There's a huge increase in tests that were not being done at all three months ago, four months ago, and a worldwide need for them. So there's supply chain challenges not just here in the U.S. but around the world,” Schuchat said. “Initially, the challenges were so much of the supply chain is China and they were needing all of the supplies themselves. And now the problem is the interdependence of these components of testing.”

Mike Weist, a spokesman for Roche Diagnostics Corporation, which has shipped hundreds of thousands of coronavirus test kits after the company’s tests were approved by the Food and Drug Administration under an emergency use authorization, said the company was keeping a close eye on its supply chain.

“We are continuously reviewing our stock position and increasing production where possible to ensure our supply chain remains robust. Due to the high demand on reagents and consumables the supply situation may be challenging in the short term in some cases,” Weist said in an email.

At times, even more basic items needed to conduct the tests have run in short supply. Earlier this month, the Defense Department flew a C-17 cargo plane full of 800,000 swabs from an Italian medical device manufacturer to Memphis, Tenn., where FedEx planes divided them among laboratories in four other states.

The problem has evolved over time, as demand for tests erupted first in China, then in South Korea and European nations, and now in the United States. The Trump administration has promised to deliver millions of tests to front-line health care facilities, though those promises have not been met.

And even if health care providers did have the millions of tests, those tests would serve little purpose if they could not be processed — the equivalent of having the ingredients to make a cake but no oven in which to cook it.

“Everyone is ramping up testing at the same time the actual availability is going down,” Osterholm said. “If you've got a run on gasoline, it doesn't matter if it's high grade or low grade or diesel.”

The growing number of different types of tests, some developed in university laboratories and others created by private companies, has helped alleviate some of the strain. Different tests use different reagents, meaning labs can draw on a broader supply than if every lab were competing for the same chemicals.

“Initially the tests that were coming out all needed the same reagents, but now there's a diversity of tests and they don't all need exactly the same component. It's one reason why there's been prioritization of who should be tested. It's not like everybody in the country should be tested every day,” Schuchat said.

The coronavirus outbreak has been met with a frenetic charge of innovation, by scientists who quickly sequenced the virus's genetic code and created different tests around the world, others who raced to create a potential vaccine that is already in its very early days of testing, and by private businesses that switched their manufacturing lines to make new protective gear or hand sanitizer.

Schuchat said the innovation in the ability to test for the virus has been equally fast. Just this week, Schuchat said a newly developed test will allow people to swab themselves, removing health care workers from that small part of the equation. New research also shows that swabs can be transported in saline, rather than chemicals that are harder to come across.