Need a COVID-19 test in Maryland? First you need to find one.

When Sheila Mahoney got a text alert that she may have been exposed to the coronavirus, the Baltimore resident spent an hour on the state’s online testing locator and then directly on pharmacy websites, finding one next-day appointment — in Virginia.

The next morning, however, she booked an appointment 15 minutes later at the Baltimore Convention Center on her phone and rushed over.

“I spent less time getting tested here than I spent looking for a test last night,” she said Wednesday after getting her nose swabbed under a big white tent outside the convention center. “I feel lucky it was open when I needed it.”

Testing at the state-run convention center testing site, open since the early days of the pandemic, was reduced to Mondays, Wednesday and Fridays after the introduction of vaccinations, but workers there still swab an average of 410 people daily.

Without a bit of luck, many Marylanders who need a COVID-19 test for work, travel or exposure are finding it increasingly difficult to get tested.

The state has closed many of its mass testing and vaccination sites as health departments shifted to more focused vaccination efforts. Over-the-counter rapid, or antigen, tests are in short supply on store shelves and online. And urgent care centers and pharmacies are overwhelmed with demand from surging cases linked to the more contagious delta variant.

It’s an issue across the nation, including Maryland, where vaccinations are relatively high and the positivity rate has for the past month hovered below 5%, an internationally established benchmark for sufficient testing.

“It’s possible to look good, but you can still have a problem if you’re not testing the right people,” said Jennifer Nuzzo, a senior scholar at the Johns Hopkins University’s Center for Health Security. “Because we pulled back on testing options, it’s like we’ve turned the telescope to another part of the sky.”

Nuzzo said the pivot from mass testing to mass vaccinations is likely causing infections to fall through the cracks. Some sites remain open, but there are often have logistical or financial barriers to getting a test.

This comes at a time when cases are high and school and job-related requirements are pushing testing demand to near the pandemic’s winter peak. Workers to run tests also are in short supply, further straining the system and delaying results.

Nuzzo said the upcoming holiday travel season could make matters worse.

Consumers already are running into issues.

When Lutherville resident Bill Gimbrede planned to visit his cousin in Boston, he and his wife decided they would take at-home COVID-19 tests before travel and after arrival. But Gimbrede said he checked 15 different pharmacies in person and online and came up empty-handed.

“I reached out to my cousin in Boston and she went out and only one was on the shelf,” Gimbrede said. “At this point, I would buy them like we did with toilet paper 15 months ago. I would buy three to four kits just to keep at home.”

Gimbrede found a PCR test in nearby Towson, though he had to wait three days for lab results, which were negative. He didn’t consider this delay too bad, but is concerned about a trip to Canada next month, a time when he expects demand to spike.

The national pharmacy chains CVS and Walgreens say they are performing millions of tests a month. CVS said there have been intermittent disruptions in its supplies. Both companies have already capped purchases of at-home tests, which can cost $25 for the rapid ones to $120 for the PCR kind.

It could take months for rapid test manufacturers to ramp up production after they scaled down over the summer when the pandemic ebbed, said Tinglong Dai, professor of operations management and business analytics in the Johns Hopkins University Carey Business School.

Abbott, maker of the popular at-home BinaxNOW test kit, said in a statement that the company has faced “unprecedented demand.” It’s hiring additional employees to ramp up production and “tens of millions more tests will be available in coming weeks and months.”

Also, the U.S. Food and Drug Administration gave authorization Monday to ACON Laboratories for its Flowflex COVID-19 Home Test, adding to the list of rapid tests on the market. The company plans to produce more than 100 million tests a month initially, potentially doubling capacity across the country in the next several weeks, the FDA said.

Until then, with at-home tests scarce, consumers are turning to urgent care centers and elsewhere.

The Maryland Department of Health’s online locator lists more than 300 testing locations searchable by ZIP code. Andy Owen, a department spokesman, said department-backed sites have not had issues securing or administering tests and can support expanded hours if local jurisdictions see fit. The state also is considering expanded hours at sites in Annapolis and Prince George’s County during the winter holidays.

“We encourage Marylanders to take advantage of state and local testing,” where tests are free, referrals aren’t needed and walk-ins largely are welcome, Owen said.

The state, however, lists far more private sites than public ones, with disclaimers about potentially pricey out-of-pocket costs or copays, requirements for referrals and testing kit shortages. Some places don’t test children under age 12, who are not eligible for vaccination.

Booking appointments can mean clicking through a maze of websites, particularly for a weekend slot.

Dai said this is what he did when his two unvaccinated young children needed testing in August.

“It was a rather confusing process and the limited information offered by the test site locator and varying hours at each site didn’t help either,” he said. “We ended up choosing a test provider that charged a $10 copay, but they also charged my insurer over $120 per test. And that’s after negotiation — they actually asked for more than $800. We were told that if we didn’t have health insurance, they would have simply charged us $20 upfront.”

Dai said the process “feels like a chaotic and crowded gray market with little coordination or regulation.” It could be better coordinated given available money, resources and technologies, he said, if there was the political will for that to happen.

Among local health departments, listings show Carroll and Harford counties no longer offer tests. Baltimore and Howard counties and Baltimore City offer weekday testing, while Anne Arundel County offers weekday and limited weekend hours.

Health officials in Anne Arundel said county sites, including a drive-through option in Glen Burnie on Saturdays, test up to 1,500 people weekly.

Baltimore City had offered testing Saturdays at the Patapsco Flea Market and through a partner at the Edgar Allan Poe House & Museum in Poppleton, but both were recently dropped from the schedule. Dr. Adena Greenbaum, who oversees the city’s testing, said officials continue working to ensure tests are available across the city most days to send the message about their importance.

City officials monitor demand at these sites, which average 30 to 90 tests a day. They track resources, staffing and logistical issues, such as bad weather at outdoor venues, so adjustments can be made. The city also launched a pilot where PCR test samples are taken in people’s homes and sent for processing.

While health departments largely scaled back testing, hospitals moved testing to affiliated urgent care and physician offices. That includes three of the state’s largest health systems, MedStar Health, LifeBridge Health and the University of Maryland Medical System.

Johns Hopkins Medicine doesn’t have its own large urgent care network and is mostly testing its own staff and patients, mostly those in its hospitals.

MedStar offers the public tests in doctors’ offices and at 33 urgent care sites. Symptomatic people can walk in, but others need appointments, which may not be available everywhere each day given high demand, said Marianne Worley, a spokeswoman.

At LifeBridge hospitals, testing also moved to urgent care centers once demand dropped with the general increase in testing availability, said Leslie Simmons, LifeBridge’s chief operating officer and executive vice president. Grace Medical Center is the only hospital to continue testing to ensure access in underserved West Baltimore.

The University of Maryland system, too, shifted appointments to its urgent care centers and physician offices. The system also helps operate the Baltimore Convention Center testing site for the state, among the first that opened in Maryland and a routine stop for those needing tests.

A steady stream of people entered the center Wednesday, including Catrice Rogers, who brought her 10-year-old daughter after she missed her weekly school-based test. Rogers said the center became her “go-to” after a frustrating tour of other sites.

She said one Baltimore church offering testing wasn’t open during advertised hours and operators of another site told her they’d stopped testing. A third site closed minutes before she arrived. Results from a drugstore where she managed to get an appointment took more than the three days she thought was acceptable.

“It’s really hard to navigate this,” Rogers said. “If the convention center isn’t open next time I need a test, I don’t know what I’ll do.”