SARS-CoV-2 Transmission Dynamics in a Sleep-Away Camp

Abstract

Objectives: In late June 2020, a large outbreak of coronavirus disease 2019 (COVID-19) occurred at a sleep-away youth camp in Georgia, affecting primarily persons ≤21 years. We conducted a retrospective cohort study among campers and staff (attendees) to determine the extent of the outbreak and assess factors contributing to transmission.

Methods: Attendees were interviewed to ascertain demographic characteristics, known exposures to COVID-19 and community exposures, and mitigation measures before, during, and after attending camp. COVID-19 case status was determined for all camp attendees on the basis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) test results and reported symptoms. We calculated attack rates and instantaneous reproduction numbers and sequenced SARS-CoV-2 viral genomes from the outbreak.

Results: Among 627 attendees, the median age was 15 years (interquartile range: 12-16 years); 56% (351 of 627) of attendees were female. The attack rate was 56% (351 of 627) among all attendees. On the basis of date of illness onset or first positive test result on a specimen collected, 12 case patients were infected before arriving at camp and 339 case patients were camp associated. Among 288 case patients with available symptom information, 45 (16%) were asymptomatic. Despite cohorting, 50% of attendees reported direct contact with people outside their cabin cohort. On the first day of camp session, the instantaneous reproduction number was 10. Viral genomic diversity was low.

Conclusions: Few introductions of SARS-CoV-2 into a youth congregate setting resulted in a large outbreak. Testing strategies should be combined with prearrival quarantine, routine symptom monitoring with appropriate isolation and quarantine, cohorting, social distancing, mask wearing, and enhanced disinfection and hand hygiene. Promotion of mitigation measures among younger populations is needed.

Figure 1.

Epidemic Curve of Symptomatic Cases (n=242^a) by Attendee Type, Number of Attendees at the Camp Over Time^b, and Key Events ^aOne additional community-associated case was missing a symptom onset date and was excluded. ^bSome trainees and staff (n=37) arrived at camp prior to orientation during June 10–16. Three staff arrived at camp on June 21 and did not attend orientation, and five campers and staff left during June 29–July 1.

Figure 2.

Attack Rates^a by Cabin^b During Orientation and Camp Session ^aThe final case status is shown for each attendee. Staff members attended both orientation and the camp session, and their final case status is shown in both periods. ^bSix cabins with three persons or less were not shown in this figure. Two of these cabins did not house any cases.

Figure 3.

Case and Instantaneous Reproductive Numbers During Orientation and Camp Session *Effective or instantaneous reproductive number could not be estimated for these dates.