A single Covid-19 positive camper set off a chain of infection that reached more than three-quarters of students, counselors and staffers at a faith-based retreat in Wisconsin over the summer, health officials reported Thursday.
Camp organizers had tried to prevent just such a superspreading by requiring proof of immunity -- an effort that failed completely, Wisconsin health officials reported in the Centers for Disease Control and Prevention's weekly health report, the MMWR.
The 152 high school-aged boys from 21 states and territories and foreign countries, counselors and staff were asked to produce negative Covid-19 tests or proof they had been infected and recovered; to self-quarantine at home for a week before traveling to the camp; and to wear masks while traveling.
Once there, the camp organizers seemed to feel free to let the boys loose.
"At the retreat, students and counselors were not required to wear masks or social distance, and students mixed freely. Classes were held in outdoor pavilions with approximately 20 students per class seated less than 6 feet apart at tables," the team, led by Ian Pray of the Wisconsin Department of Health Services, wrote.
"Beds in dormitory rooms and yurts were tightly spaced with three to four sets of bunks each, shared bathrooms, and shared common areas."
By the second week of the camp, 24 students were displaying symptoms, and two had tested positive for Covid-19. Still, camp staff did little to contain the spread.
"These students were given masks, but contact tracing was not done and the students were not isolated," the researchers wrote.
After the second positive test result, the Wisconsin Department of Health Services stepped in. It was almost too late to stop the virus, however.
"At least one confirmed case occurred in every dormitory room and yurt," the researchers wrote. In all, 118 people tested positive -- 78% of campers and staff. This was likely an underestimate, the researchers said, because testing was done well after the outbreak started.
Only one of the four staff members got sick -- they all had individual sleeping quarters.
Of interest, almost all the infected campers had symptoms, and those who had been infected before they came to camp showed no evidence of becoming infected a second time.
"This outbreak investigation documented rapid spread of SARS-CoV-2, likely from a single student, among adolescents and young adults in a congregate setting," Pray's team concluded.
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