Visitors gather at Sand Beach in Acadia National Park in late June. Brianna Soukup/Staff Photographer

Physicians at Mount Desert Island Hospital believe at least 35 out-of-staters carrying COVID-19 have been on the island this summer and could have spread the disease in the community.

The Bar Harbor hospital sounded a public warning about the situation Friday, but had not said how many people it thought were involved. The estimate from the hospital’s front-line medical personnel includes people with positive test results and people presumed positive because they were in the same traveling party as an infected person. Because the affected people took tests in their home states, all 35 have been essentially invisible to state and local authorities through official channels.

Because of crippling one-to-two-week delays at the major national test processors, the people involved didn’t learn they had tested positive until they were already traveling in Maine. The hospital learned of their presence only when the infected individuals phoned it for advice.

“Our physicians and care practitioners on the front lines of our COVID-19 testing and counseling efforts estimate that there are 35 individuals and families or more who are potential spreaders – either because one of the family members is positive and they all traveled together or because they met family or friends on MDI before receiving a positive result,” spokesperson Oka Hutchins said by email.

Dr. Julius Krevans Jr., the hospital’s chair of infection prevention, said Monday that the situation presents a real threat.

“Persons with out-of-state addresses with (the coronavirus) are a particular concern of mine. The failure to acknowledge, track and trace these individuals has both direct and indirect public health fallout,” Krevans said by email. “Maine, by virtue of both its geography and excellent state leadership, has done very well so far, but this situation represents a clear and present danger that should be addressed.”

The problem has apparently been building for weeks, and the hospital has been trying to establish a partnership with the Maine Center for Disease Control and Prevention to organize timely contact tracing using local resources. The official U.S. practice is for public health officials in an infected person’s home state to organize the tracing of their contacts, even if most of those contacts took place hundreds or thousands of miles away in Downeast Maine.

Hutchins said the hospital recognizes that the Maine CDC is managing multiple challenges and because of that has been offering local resources to partner with the agency to contact trace. The hospital also wants the agency to register the infected individuals in the Sara Alert system, a tool used by Maine and several other states to allow COVID-19-positive individuals to report their symptoms and help medical providers contact trace among their own staff.

“To address this, we need the support of the Maine CDC and their network of contract tracers to follow these individuals and enroll them into the Sara Alert system,” Hutchins said. “One of the ideas that we floated earlier this summer is potentially asking retired clinicians regionally and statewide to help call and trace.”

Asked about the Maine CDC’s response to the situation, agency spokesman Robert Long said via email that MDI Hospital has log-in credentials to the Sara Alert system and could add contact information on the individuals themselves, “regardless of place of primary residence.” As of Monday morning, he said, there “is no indication that anyone from MDI Hospital had completed the training to use the Sara Alert system.”

Asked about this, Hutchins said: “Our understanding of the Sara Alert system is that it would not provide what we need to address this issue, but we will seek guidance from the CDC on potential opportunities to do so.”

Long also said the Maine CDC has worked since March to help health care providers and hospitals prepare for such situations, and would continue to do so. “Communication among all parties is essential in all aspects of the state’s pandemic response,” he wrote.

He also noted that nonresidents are supposed to quarantine upon arrival in Maine until they receive their test results – though this is not true of residents of Connecticut, New Hampshire, New Jersey, New York and Vermont, whom Gov. Janet Mills exempted because of the low prevalence of the disease in those states.

“Maine CDC encourages people from other states who receive delayed positive test results from their home states to continue checking in with medical providers in Maine as a way of helping to ensure that local health care systems have the most complete information on potential transmission in their communities,” Long said.

That’s exactly how the Bar Harbor hospital learned of the presence of the nonresidents infected with COVID-19: They called for advice after receiving their test results. In a statement on its Facebook page Friday, the hospital encouraged out-of-state visitors in the same situation to contact them, and said it was providing counseling and contact tracing assistance for those it heard from. (The number for this is 207-801-5900.)

The hospital has been at the center of a community-wide effort to regularly test hundreds of front-line tourism workers such as cashiers, hotel clerks and servers, as well as tourists, and provide them with masks. Last week it processed three positive COVID-19 tests, all from people who reside outside of Hancock County after having had no positives since May 16.

“Our community and our state have done a very good job of keeping COVID-19 precautions in place, and because of this, the incidence of COVID-19 in our community has remained low,” the hospital said in its statement. “We urge all residents and visitors to remain vigilant in their COVID-19 precautions – masking, physical distancing and handwashing continue to be the best tools we have to slow the spread of COVID-19.”

As of Wednesday, no residents of Bar Harbor had tested positive, according to the Maine CDC’s zip-code-level data, and the towns of Mount Desert and Southwest Harbor each had between one and five cases. As of Sunday, Hancock County as a whole had 34 resident cases, 15 of them added after July 28, a period when outbreaks were confirmed at blueberry businesses in the towns of Ellsworth and Hancock.

The proportion of COVID-19 tests from out-of-staters that are coming back positive in Maine has increased throughout July, with nonresidents now testing positive in Maine at a rate more than four times that of residents. For the month as a whole, there were 57 positive tests of non-residents reported to the CDC out of the 1,773 taken, a positivity rate of 3.2 percent, though the rate has been over 4 percent since July 19.

It isn’t clear whether the challenge affecting MDI is happening elsewhere in the state. Spokespeople for the two largest hospital networks in the state, Maine Health and Northern Light Health, said they don’t routinely compile such information and were not aware of any specific instances, though they said it was possible they had occurred.

York Hospital, which serves tourism-intensive York County, doesn’t track it either, but one of their infectious disease physicians, Dr. Evangeline Thibodeau, said Friday via email that anecdotally, she had heard of such scenarios “many times.”