“The availability of those reagents is obviously being looked at,” he said, referring to the chemicals used for preparing samples. “I’m confident of the actual test that we have, but as people begin to operationalize the test, they realize there’s other things they need to do the test.”

The coronavirus task force convened by the White House is also aware of the shortages, and one official said members are working on it.

The growing scarcity of these “RNA extraction” kits is the latest trouble for U.S. labs, which have struggled to implement widespread coronavirus testing in the seven weeks since the country diagnosed its first case. Epidemiologists and public health officials say that the delayed rollout, caused in part by a botched CDC test, has masked the scope of the U.S. outbreak and hobbled efforts to limit it.

If enough processing kits aren’t available, the risk that testing will be disrupted is “huge,” said Michael Mina, associate medical director of molecular diagnostics at Brigham and Women's Hospital in Boston.

“RNA extraction is the first step in being able to perform” a coronavirus test, he said. “If we cannot perform this step, the [coronavirus] test cannot be performed.”

Qiagen, a major supplier of the kits, confirmed that its product is backordered due to “the extraordinary pace” at which the world has increased coronavirus testing over the last few weeks.

Public health labs across the U.S. have tested more than 5,000 people, according to the Trump administration. HHS Secretary Alex Azar told lawmakers on Tuesday that U.S. labs’ capacity could grow to 10,000-20,000 people per day by the end of the week.

“Increased demand for testing has the potential to exhaust supplies needed to perform the test itself,” said Robin Patel, president of the American Society for Microbiology. That would limit the testing capacity of public health, hospital and commercial labs alike, she added.

Complicating the situation, most labs have been running at least two tests per patient — although that could soon change. The CDC issued interim guidelines on Monday that minimize the number of tests required for a diagnosis. The agency says labs can combine a patient’s nose and throat samples into one test, a move experts say will cut in half the amount of supplies used to test each person.