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4 camps prevented Covid-19 outbreak in over 1K people via testing, here's what schools can learn from findings

A multi-layered strategy was successful in identifying and isolating 3 asymptomatic Covid-19 cases and preventing secondary transmission, which may be considered in settings such as schools and colleges, say experts
(Getty Images)
(Getty Images)

As schools and public health experts look for ways to safely bring back students into classrooms, researchers show how a multi-layered approach of pre-arrival quarantine, testing, and isolation, among others, helped prevent Covid-19 transmission in overnight camps in the US. During the 2020 summer camp season, four Maine overnight camps with 1,022 attendees from 41 states and international locations implemented a prevention and mitigation strategy that was successful in quickly identifying and isolating three asymptomatic Covid-19 cases and preventing secondary transmission, says a report by the US Centers for Disease Control and Prevention (CDC).

“In a time when we hear so many stories of what doesn’t work to contain coronavirus, here is a story of what can work. Diligent use of layered measures helped to prevent outbreaks of Covid-19 at four overnight camps in Maine among over 1,000 campers and staff arriving from 41 states and seven international locations. Pre-arrival screening and testing identified 16 attendees who were Covid-19 positive, and testing after camp arrival revealed three asymptomatic positive individuals. No secondary infections were identified,” lead author of the report, Dr Laura L Blaisdell, told MEA WorldWide (MEAWW). She is from the Center for Outcomes Research and Evaluation, Department of Pediatrics, Maine Medical Center Research Institute and Maine Medical Center, Portland, Maine.

“These findings demonstrate diligent use of multi-layered public health strategies to be successful in an overnight camp setting to prevent the spread of Covid-19. While we need to be careful about this application to other settings, this approach may be considered as schools and colleges return to in-person settings,” Dr Blaisdell told MEAWW.

What strategies were implemented?

During June-August, the combined attendance of the four camps included 642 children and 380 staff members, aged 7-70 years. The camp sessions ranged from 44 to 62 days (including a 14-day staff member orientation) during June 15-August 16. To prevent, identify, and mitigate the spread of coronavirus, the four Maine overnight summer camps with similar size, session duration, and camper and staff member characteristics opened with uniform nonpharmaceutical interventions (NPIs), including pre-camp quarantine, pre- and post-arrival testing and symptom screening, cohorting, and physical distancing between cohorts. Camps required the use of face coverings, enhanced hygiene measures, enhanced cleaning and disinfecting, maximal outdoor programming, and early and rapid identification of infection and isolation.

Camps required the use of face coverings, enhanced hygiene measures, enhanced cleaning and disinfecting, maximal outdoor programming, and early and rapid identification of infection and isolation (Getty Images)

All attendees were instructed to quarantine with their family unit (unless parents were essential workers) for 10-14 days before camp arrival. Approximately 5-7 days before camp arrival, 1,010 of the 1,022 attendees were tested for Covid-19. The remaining 12 attendees who had completed a period of isolation after receiving a diagnosis of Covid-19, two months before arrival, were not tested. The rest of the 1,006 attendees received negative Covid-19 test results. Three of four camps mandated submission of test results before camp entry, and delays in receipt of test results caused one camp to isolate 15 campers until negative results were known, up to 4 days after camp arrival. To address potential late exposures or exposures during travel, all camps quarantined attendees by cohort or group for 14 days after camp arrival, regardless of testing or screening results. “Testing and quarantine before staff member and camper arrival were essential to identifying Covid-19 infection and preventing the introduction of the virus into these congregate settings of younger adults who might be only mildly symptomatic or presymptomatic,” the investigators explain.

After camp arrival, campers and staff members were screened by health staff members at least daily (at one camp twice daily) for fever and through direct questioning for symptoms consistent with Covid-19. Changes to usual camp activities included limiting indoor activities that mixed cohorts, staggering dining periods or dining outdoors, group-specific programming, and limiting sports to those that allowed for physical distancing between staff members and cohorts. Stable groups were based on living quarters (such as bunk assignment) or age division and ranged in number from 5-44 people. If interacting outside the group, individuals were required to wear face coverings and maintain a physical distance of 6 feet for a minimum of 14 days.

The report says that four asymptomatic people received positive Covid-19 test results before arrival and delayed their arrival. They were isolated for 10 days at home, remained asymptomatic, and did not receive any further testing before arrival or for the duration of camp attendance. Daily symptom checks identified 12 attendees (one staff member and 11 campers) with signs or symptoms compatible with Covid-19. They were immediately isolated and tested, and their groups were quarantined until test results were available. All 12 isolated attendees received negative test results, after which isolation and cohort quarantine were discontinued. 

After camp arrival, campers and staff members were screened by health staff members at least daily (at one camp twice daily) for fever and through direct questioning for symptoms consistent with Covid-19 (Getty Images)

According to the researchers, three asymptomatic attendees at three different camps (two staff members and one camper) tested positive for Covid-19 after arrival at camp and were rapidly isolated and their groups (sized five, six, and 30 attendees) were quarantined for 14 days. Both asymptomatic staff members isolated for 10 days and received negative test results twice, 24 hours apart, at the end of their isolation. The asymptomatic camper was isolated on day three after testing when positive test results were received. The camper was retested on days four and five after a positive test result and released from isolation on day eight after a second negative result was received. “The 30 members of the camper’s cohort were retested on days three and four after the asymptomatic camper’s initial positive test result. No cohort members received a positive test result, and all were released from quarantine on day eight after the asymptomatic camper’s positive test result. No secondary transmission was identified,” write authors. 

The Maine camps’ experience contrasts with that of an overnight camp in Georgia where 260 children and staff members out of 344 tested, got infected with Covid-19. The CDC reported that among 136 cases with available symptom data, 26% reported no symptoms, suggesting that asymptomatic transmission may have played a role. The researchers of the current study say that while no single intervention can prevent Covid-19 transmission, the multi-layered use of NPIs allowed camps to prevent spread and quickly identify campers or staff members with coronavirus infection to successfully mitigate spread.

“Camps did not rely on testing as a sole NPI. Notably, stable, small, segregated cohorts allowed camps to isolate and quarantine a wide age range of younger attendees with potential Covid-19 symptoms and exposures while continuing camp operations in other cohorts,” they write. The team emphasizes that the findings can inform similar multi-layered public health strategies to prevent and mitigate the introduction and transmission of Covid-19 among children, adolescents, and adults in congregate settings, such as overnight camps, residential schools, and colleges. 

“Using a combination of proven public health strategies to slow the spread of Covid-19, campers and staff were able to enjoy a traditional summer pastime amid a global pandemic. As communities work together to get us back to where we used to be, it is essential that everyone – for their good and that of their family’s – follow CDC and the federal government’s recommendations to protect against Covid-19. This includes wearing masks, practicing social distancing and good hand hygiene, and staying home when you are sick,” recommends CDC Director Dr Robert Redfield.