In July 31, 2018 file photo, visitors to Maine's Acadia National Park gather to watch the sunrise on top of Cadillac Mountain. Credit: Robert F. Bukaty | AP

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The hospital closest to the tourist hot spot Acadia National Park is warning that there are likely undetected cases of the coronavirus in the area, which millions of travelers visit each year.

Mount Desert Island Hospital said Friday that it’s only recently recorded its first positive test results in several months, and that it’s heard from out-of-state visitors who were tested in their home state but didn’t receive their results — which were positive — until they had arrived in Maine.

“We are receiving calls from visitors — both tourists and family members of area residents — who were tested before traveling and only received positive results after their arrival here,” the hospital said in a Facebook post. “And these visitors’ test results are not captured by current reporting requirements.”

Maine requires that out-of-state visitors quarantine for 14 days upon arriving in the state. Alternatively, they don’t have to quarantine if they’ve tested negative within 72 hours before they arrive in Maine.

But national delays in coronavirus test processing mean many visitors aren’t receiving results until after their arrival. Those positive results then aren’t recorded in local testing data.

Visitors who haven’t received a test result before arriving in Maine are expected to quarantine until they receive a negative test, but MDI Hospital didn’t say whether the visitors it has heard from had quarantined.

The U.S. Centers for Disease Control and Prevention currently requires that all positive cases be recorded in a person’s state of residence, regardless of where they’re tested. As a result, positive test results among out-of-state visitors aren’t added to Hancock County’s or Maine’s case totals.

Although Hancock County has seen two coronavirus outbreaks in the past week at blueberry processing and farming operations, the county has had low case numbers throughout the pandemic. As of late Thursday, it had seen 27 cases since March, and it was the county with the fourth lowest rate of infections in the state.

But that doesn’t mean the virus isn’t circulating undetected as more people visit the area for the summer tourist season, according to Mount Desert Island Hospital.

The hospital’s COVID-19 team is providing counseling and contact tracing assistance when the hospital receives calls from out-of-state visitors about positive test results. But it has no way to track cases if visitors don’t reach out.

The hospital’s testing for the coronavirus is generally limited to those with symptoms and a doctor’s order to receive a test. But it is providing testing to asymptomatic people working in the tourism industry through a partnership with the Downeast COVID-19 Task Force.

The goal of the partnership is to detect any potential COVID-19 outbreaks. So far, according to the hospital, no one tested through the program has received positive results.