In this June 2020 file photo, trip leader Gordon Anderson power washes an outdoor basketball court at the Camp Winnebago summer camp in Fayette, Maine. Credit: Robert F. Bukaty | BDN

Four Maine summer camps could have been like a giant petri dish for the coronavirus when they opened two months ago.

They drew 1,022 people ― staffers and campers ― from 41 states, one territory and six foreign nations. But after several weeks, only seven campers and staff tested positive for COVID-19 among the four camps, and one of those was a false positive.

A new study from the U.S. Centers for Disease Control and Prevention released Wednesday said that the four summer camps, whose names aren’t revealed, did so well at preventing the spread of coronavirus that they could serve as a model for other, similar enterprises such as schools.

The camps employed “a multilayered prevention and mitigation strategy” that greatly hindered the spread of the disease, according to the study, published in the CDC’s Morbidity and Mortality Weekly Report. Camps elsewhere weren’t so careful, with the coronavirus infecting hundreds at a Georgia camp that didn’t require the use of face coverings.

“These findings have important implications for the successful implementation of COVID-19 mitigation strategies in other overnight camps, residential schools, and colleges,” the study said.

The $26 billion summer-camp industry was hit hard by the virus. About 82 percent of the 8,947 U.S. overnight camps did not operate, and in Maine, only about a fifth of the state’s 100 overnight camps opened this year, according to the study.

The U.S. has about 15,000 day and overnight camps employing 1.5 million staff members and hosting some 26 million children annually. Maine hosts 20,000 to 25,000 American and foreign children annually, according to the study.

In this Thursday, June 4, 2020 photo, a row of cabins will soon be occupied by campers at the Camp Winnebago summer camp in Fayette, Maine. The boys camp is going ahead with plans to open with a reduction in the number of campers and other changes to comply with guidelines for helping prevent the spread of the coronavirus. Many of the nation’s 15,000-plus summer camps opting to close because of health concerns surrounding the pandemic, or because of delays in receiving rules or guidelines from licensing officials. Credit: Robert F. Bukaty | AP

The four camps followed their nearly identical and multilayered routines vigorously. They tested everyone upon arrival at camp, enforced the use of face coverings and maintenance of physical distancing and had their staff and guests practice enhanced personal hygiene. They improved their cleaning and disinfecting routines and kept their staff and campers in outdoor settings as much as possible, according to the study.

Five to seven days prior to going to camp, 1,010 of the 1,022 attendees were tested for COVID-19 by their doctors or at commercial laboratories. Three of four camps made review of test results mandatory before accepting attendees. Delays in handing over results caused one camp to isolate 15 campers up to four days after arriving, until their test results were submitted, according to the study.

Of the 1,010 who were tested prior to coming to camp, 12 attendees who had been diagnosed with COVID-19 were kept in isolation before they arrived. Four attendees who tested positive for COVID-19 but were asymptomatic delayed coming to camp and instead isolated themselves for 10 days at home.

Once they got to their camps, all attendees were kept in groups according to their age for 14 days after they arrived, and after the first week, the 1,006 attendees without a previous diagnosis of COVID-19 were tested. When three asymptomatic cases were identified, they and the people they came in contact with immediately went into quarantine at their camps, and no further transmission of the virus occurred with them, according to the study.

All attendees had their temperatures taken at least once a day and groups were kept to fewer than 50 members, with some groupings as small as five people, so any viral spread would be contained.

One of the studies’ authors, Laura L. Blaisdell, told the Portland Press Herald that the multilayered approach was crucial to the camps’ success.

“You can’t pick or choose one strategy. You have to layer several strategies all day every day, every layer to have the best success. We know we can’t provide a COVID-free environment,” Blaisdell said.