How Four Maine Summer Camps Kept COVID-19 from Spreading, 2020

This page describes the summer of 2020, before COVID-19 vaccines, and the precautions and isolation rules of that time.

After the World Health Organization declared COVID-19 a pandemic on March 11, 2020, closures of 124,000 U.S. public and private schools affected at least 55.1 million students through the end of the school year. That summer about 82% of the country's 8,947 overnight camps did not open, and in Maine only about 20% of 100 overnight camps did. A camp in Georgia had seen the virus spread among campers and staff when prevention measures were not strictly followed. Four overnight camps in Maine opened with a layered set of prevention measures, and physicians and researchers from Maine Medical Center, the University of Virginia and elsewhere reported the results in CDC's Morbidity and Mortality Weekly Report.

Summer camps are a $26 billion industry: about 15,000 day and overnight camps employ about 1.5 million staff and host an estimated 26 million children a year. Maine's licensed camps serve 20,000–25,000 children from the United States and abroad each year.

The camps

From June 15 to August 16, 2020, the four camps, similar in size, session length and population, ran single sessions of 44 to 62 days, including a 14-day staff orientation. They hosted 1,022 people, 642 children and 380 staff members, from 41 states with a wide range of infection rates, plus Puerto Rico and six other countries (Bermuda, Canada, Mexico, South Africa, Spain and the United Kingdom). Camps did not restrict where attendees came from.

Layers of protection

No single measure can stop the virus, so the camps stacked many:

• Before camp: attendees quarantined with their families for 10–14 days (families of essential workers limited contact with the camper instead) and were tested by RT-PCR. Travel directly to camp by family car was preferred; bus riders and air travelers wore face coverings.
• Arrival: all attendees were quarantined by group for 14 days after arrival, whatever their test results, to cover exposures during travel.
• Cohorts: campers lived and did activities in stable groups of 5 to 44, based on cabin or age. Outside their group they wore face coverings and stayed 6 feet apart for at least the first 14 days. Bathrooms were assigned or staggered by group.
• Daily screening: health staff checked everyone for fever and symptoms at least once a day.
• Hygiene and cleaning: hand cleaning before and after every activity and meal; frequent disinfection of high-touch surfaces and shared equipment; bathrooms cleaned twice a day; single-use items where possible.
• Outdoors: indoor activities that mixed groups were limited, meals were staggered or outside, and only sports allowing distance between groups were played.
• Staff stayed on site for the whole session, with no days off away from camp.

No attendee had a condition that prevented wearing a face covering, and all were observed to follow face covering and distancing rules.

What testing found

Before arrival: 1,010 of the 1,022 attendees were tested; the other 12 (nine staff and three campers) had had COVID-19 with symptoms in the previous 2 months and completed isolation. Four attendees (0.4%) tested positive without symptoms. They delayed their arrival, isolated at home for 10 days and came to camp afterward. The other 1,006 tested negative. Delays in results led one camp to isolate 15 campers for up to 4 days after arrival until their negative results came in.

At camp: daily checks flagged 12 attendees (1.2%) with possible symptoms. Each was isolated and tested and their group quarantined; all 12 tested negative, and everyone returned to normal camp life. About a week after arrival, all 1,006 attendees without a previous diagnosis were tested again, and none declined. Three people without symptoms (0.3%), two staff members and a camper at three different camps, tested positive. They were isolated at once and their groups, of 5, 6 and 30 people, quarantined for 14 days. The camper's group of 30 was retested on days 3 and 4 and all tested negative. No one caught the virus at camp.

Why it worked

Testing and quarantine before arrival kept the virus from getting in, which mattered because young people may have only mild symptoms or none. Timely results, strict quarantine, precautions while traveling and careful precautions in the first two weeks were all important. Small, stable groups let the camps isolate and quarantine a few people at a time while the rest of camp carried on, and the camps did not rely on testing alone.

The authors note limitations: adherence to each measure was not measured; not testing everyone at the end of sessions may have missed silent spread; all four camps ran single sessions; attendees may have traveled through places other than their home state; and the low number of infections makes the measures more likely to have worked for at least some time. They also caution that prearrival quarantine and testing, quick results, cohorting and on-site isolation may not be practical everywhere. Still, they conclude that such layered strategies can work in overnight camps, residential schools and colleges.

Sources

• Blaisdell LL, Cohn W, Pavell JR, Rubin DS, Vergales JE. "Preventing and Mitigating SARS-CoV-2 Transmission — Four Overnight Camps, Maine, June–August 2020." MMWR 69(35). https://www.cdc.gov/mmwr/volumes/69/wr/mm6935e1.htm
• The report describes attendees as aged 7–70, but also says the camps were for children aged 8–15; this page gives neither age range. Its figures are not reproduced here because its authors are not federal employees. Two authors reported serving as camp physicians or medical director.