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Preventing and Mitigating SARS-CoV-2 Transmission – Four Overnight Camps, Maine, June-August 2020

Our take —

In contrast to a recent report of high attack rates of SARS-CoV-2 among children and staff in a Georgia overnight summer camp, this report of over one thousand attendees of four Maine overnight camps did not identify any secondary transmissions after three asymptomatic attendees (among over one thousand) showed evidence of infection by PCR during camp. Protocols included mandatory PCR testing for all attendees in the week prior to the beginning of camp, daily symptom screening, one follow-up PCR test roughly a week after the beginning of camp, isolation of suspected cases, quarantine of exposed cohorts, and multiple other non-pharmaceutical interventions during camp activities. The report suggests that strong testing and isolation protocols can prevent significant secondary transmission of SARS-CoV-2, even in a congregate setting with multiple close contacts, when there are a small number of initial cases.

Study design


Study population and setting

This report describes non-pharmaceutical interventions to limit spread of SARS-CoV-2 among 1,022 campers and staffers (63% campers, 37% staff members; 54% female) in four overnight summer camps in the U.S. state of Maine from June 15 to August 18, 2020. Attendees and staff ranged in age from 7 to 70 years old, and were from 41 U.S. states (98%) and 6 international locations (2%). The numbers of attendees in the four camps ranged from 202 to 287, and the duration of each camp ranged from 44 to 62 days. PCR testing for SARS-CoV-2 infection was required prior to camp arrival for attendees (testing ranged from 2-9 days before the start of camp). Upon arrival, all attendees were quarantined by cohort (ranging in size from 5-44 campers) for 14 days after arrival. Attendees were screened at least once daily for fever (with an infrared thermometer) and other symptoms (verbally). Attendees were tested again with PCR (4-9 days after arrival, with results available 2-3 days later). Those with symptoms or with a positive test result were isolated, and their cohort was quarantined, until a negative test result was obtained. Attendees were instructed on hygiene and were required to wash hands with soap and water or use hand sanitizer (minimum 60% ethanol or 70% isopropanol) after all activities with a high degree of touching, including meals. Other modifications to camp protocols included requiring mask use and 6-foot physical distancing for any mixed-cohort interaction, limiting indoor mixed-cohort events, restricting sports to those permitting physical distancing, providing cohort-specific bathrooms (or staggering use by cohort), and enhanced cleaning and sanitizing. Protocols were enforced by camp staff members, and no staff member left the camp during time off.

Summary of Main Findings

Of the 1,022 attendees, 12 had received a prior diagnosis of COVID-19 and had completed their isolation over two months before camp began; they were not subsequently tested. Of the 1,010 attendees initially tested via PCR for SARS-CoV2 infection, four (0.4%) asymptomatic individuals tested positive, completed 10 days of isolation at home, did not develop symptoms, and were allowed to attend camp with no further testing. The remaining 1,006 attendees were subject to one repeat PCR test while attending camp. Three (0.3%) asymptomatic attendees (two staff members and one camper) tested positive. The two staff members were isolated for 10 days and received two consecutive negative results at the end of their isolation. Their cohorts (n=5, n=6) were quarantined for 14 days. The infected camper was isolated for 8 days and released after a second negative test result; the 30 cohort members of the camper were tested 3-4 days after the initial positive result. Quarantine for the camper’s cohort ended when the camper was released from isolation. There were no secondary infections identified. Screening identified 12 individuals with symptoms consistent with COVID-19; these individuals were isolated and tested and their cohorts were quarantined. All 12 received subsequent negative test results.

Study Strengths

Protocols were fairly well described. The study population was large, represented a wide range of ages, and came from diverse regions within the United States.


There was no measurement of adherence to NPIs. The report does not state whether the cohorts of the two infected staff members were subsequently tested. Attendees were not tested at the end of camp, so some secondary transmission may have been missed. Since all cases were asymptomatic and positivity rates were so low, it is conceivable that cases were false positives, and that no attendees were infectious upon arrival at camp. If so, no conclusions could be drawn about the effectiveness of the NPIs during camp.

Value added

This report highlights the potential benefit of rigorous testing and isolation protocols in minimizing secondary transmission of SARS-CoV-2, despite repeated long-duration contact in an overnight setting.

This review was posted on: 9 September 2020