Gov. Larry Hogan said Monday that Maryland is expanding testing for the new coronavirus by taking steps including collecting samples at several drive-thru sites.

But weeks after the first cases were confirmed, the general public still can’t drive up and request a test, according to state officials and those doing the testing. A doctor’s order is necessary.

“Testing is only for individuals with physician orders who meet specific protocols from the Centers for Disease Control and the Maryland Department of Health,” said Michael Schwartzberg, a spokesman for the University of Maryland Medical System, which is the latest to begin testing patient samples outside the state-run lab in East Baltimore.

The protocols call for testing of hospitalized patients with symptoms, and symptomatic people outside the hospital who are considered high risk, include those in nursing homes, in long-term care facilities or who have underlying health conditions. Medical personnel, health care workers and first responders with symptoms also are being tested.

Those with mild symptoms of the COVID-19 illness caused by the virus are encouraged to notify their doctor but isolate themselves and self-treat at home unless they start having trouble breathing. Health experts believe there are many more cases than those currently confirmed by testing.

Testing remains limited because the state continues to face a shortage of testing supplies, said Fran Phillips, deputy state secretary for public health services during a morning news conference at which Hogan issued a stay-at-home order for everyone in the state.

“The availability and speed for COVID-19 testing is an absolute health care industry priority across the country,” Schwartzberg said.

The university health system now can perform some diagnostic testing at five of its 13 hospitals, including the flagship University of Maryland Medical Center in Baltimore and others in Cheverly, Glen Burnie, La Plata and Towson. Its capacity is expected to continue growing as supplies increase, officials said. The system’s Upper Chesapeake Medical Center was also among the first to open a drive-thru station to take swabs for testing.

John Hopkins Hospital began diagnostic testing about two weeks ago, and others, including LabCorp and Quest Diagnostics, are testing samples collected at Maryland hospitals and elsewhere in some of its labs.

The state Department of Health reported Monday that Maryland had run fewer than 15,000 tests for the related disease COVID-19, confirming infections in just over 1,400 people in a state with a population of about 6 million.

The relatively slow pace of testing is not unusual in the United States, where testing has lagged behind some other countries. The U.S. Centers for Disease Control and Prevention bungled development of the initial test and catching up there and at private labs has been slow as supplies have been limited.

Since the first three cases were confirmed March 6, testing has shown about 45% of the state’s 1,413 cases as of Monday have been in the Washington, D.C., suburbs.

Hogan noted in Monday’s conference that the cases are not all among seniors. He said 51% of all positive cases involve people who are age 50 and younger and 56% of hospitalizations involve people younger than age 60.

To prevent more cases, Hogan has joined several other states ordering most everyone to stay home and away from others who could be infected and do not know. Many people are asymptomatic and others don’t show symptoms such as fever, cough or shortness of breath for days.

“This virus and this disease is sneaky,” Phillips said. “What you do today, what you do tomorrow, matters.”

It’s unclear when the availability of testing will expand, which health officials consider important to understanding the virus and how to stem its spread.

More expansive testing would help “situational awareness,” said Justin Lessler, an associate professor in the Johns Hopkins Bloomberg School of Public Health’s department of epidemiology.

That means understanding just how much disease is out there or how much was out there.

He said that can help show policymakers whether social distancing fails to stem the spread and whether other measures are necessary, something that should be clear in two to three weeks as those who are just infected become sick enough to head to the hospital.

Widespread testing also can show that measures are working and restrictions can be lifted. Then testing could be used to aggressively identify people who are infected so they, and anyone they’ve come in contact with, could be isolated rather than the public generally, Lessler said.

“We’re not there yet,” he said of widespread testing. “I know capacity is building fast.”

While the state is now releasing more data on how many tests are being performed, officials haven’t said how fast testing is expected to ramp up.

Johns Hopkins began testing about two weeks ago, and it’s now testing about 500 to 600 samples a day, with results in about 24 hours, said Dr. Karen Carroll, director of the division of medical microbiology at the Hopkins School of Medicine.

She said supplies of materials for testing are sufficient and she expected the lab to reach 1,000 a day in the next week. Hopkins had hoped the lab also could offer more rapid testing on other platforms, however, “kits are in high demand and inventory is low,” Carroll said.

Most hospitals are now able to take samples to send to labs. The samples taken at the state’s drive-thru sites will add to the workload at those labs.

The sites include Motor Vehicle Administration emissions stations in Bel Air, Glen Burnie and Waldorf, as well as another at FedEx Field in Landover.

They, too, will be “strictly limited” to those with doctor’s orders and an appointment, Hogan said.