A Centers for Disease Control and Prevention (CDC) case study released Thursday found that one ninth grade boy, who tested PCR negative before traveling, likely spread COVID-19 to over 100 people at a boys’ overnight summer school retreat in Wisconsin.
Among the 152 high school aged boys, counselors and staff members, there were 118 confirmed COVID-19 cases and 38 probable cases, the CDC said.
The tightly packed students, in session from July 2 to Aug. 11, didn't wear masks and shared dorms with beds close together.
The ninth grade boy who likely set off the spread had a negative PCR test less than a week before the retreat, but he developed symptoms the day after arriving, according to the CDC. A family member of the boy tested positive while he was at the retreat.
In order to lower the risk in this type of setting, the CDC said it is critical to implement pre-arrival quarantine and testing, symptom monitoring, early identification and isolation of cases, mask use, distancing and enhanced hygiene and disinfection practices.
ABC News’ Eric Strauss contributed to this report.