The Food and Drug Administration announced on Saturday that it was giving laboratories and hospitals across the country the go-ahead to conduct tests, and on Sunday, Vice President Mike Pence said the federal government released 15,000 testing kits over the weekend, and was working with a “commercial provider” to distribute 50,000 more soon.

The expansion of testing swiftly turned up new cases. “What prompted us to start looking is a change in the testing criteria,” said Dr. Francis Riedo, an infectious diseases specialist at EvergreenHealth, a public hospital district in northern King County and southern Snohomish County.

Dr. Riedo said that the positive tests among hospital patients in Washington were “the tip of the iceberg” — the most severely ill patients were being tested, but many others with less severe illness could be out in the community with undetected infections.

Dr. Scott Lindquist, epidemiologist for communicable diseases with the Washington State Department of Health, said that he was aware of cases in which physicians suspected coronavirus and could not get the patients tested before the change in criteria, though he did not know how many such cases there had been. Dr. Lindquist said the state laboratory was rapidly ramping up to be able to perform 200 tests a day.

“We’re really aggressively sampling in Washington State now, because we feel like it has been here and we haven’t had the ability to lab test,” Dr. Lindquist said.

Dr. Delaney Ruston, a primary care physician in Seattle, said she had seen a patient last week with a low-grade fever who had been in China about three weeks earlier. She said public health officials told her the patient did not meet criteria for testing because the patient had been away from China for more than two weeks. Even so, Dr. Ruston wondered whether the patient, who wore a mask in the clinic to protect others and had no cough, could have had a mild case of the illness.

“All of us are in dire need for a point-of-care test,” she said, meaning a test that can be performed quickly on site, like those now in use for seasonal influenza.