A Morbidity and Mortality (MMWR) report today documents extensive and rapid spread of COVID-19 among students and staff at a Jul 2 to Aug 11 overnight summer high-school retreat in Wisconsin where participants had prolonged contact and shared sleeping quarters.A single student who tested negative for SARS-CoV-2 within the week before the retreat was the likely source of the outbreak that infected 76% of attendees, according to the report's authors, who are from the Wisconsin Department of Health Services (WDHS), the Centers for Disease Control and Prevention, and several US universities.Several pre-camp precautionsTo mitigate the spread of COVID-19, retreat organizers required 152 attendees traveling from 21 states to provide documentation