A coronavirus outbreak ravaged through a summer high school retreat in Wisconsin this summer, after one student developed symptoms and infected 91 per cent - or 116 - of the students and counselors.
The astonishing outbreak was discussed in a new Center for Disease Prevention and Control study published Thursday.
The 'superspreading' event happened at a faith-based educational retreat for high school-aged boys in grades nine to eleven, which took place between July 2 and August 11.
The retreat included 152 boys, counselors, and staff members that arrived from 21 states and territories and two foreign countries. Each person was required to undergo testing and quarantine the week prior to the camp.
But one ninth grader, who had tested negative while at home, began developing symptoms shortly after his arrival.
The teenager was administered a PCR test that came back positive. Soon, the virus would rip through the retreat as precautions fell to the wayside.
According to the CDC, the Wisconsin Department of Health Services was alerted of the concerning outbreak on July 25.
Three days later, department officials tested 148 of the 152 attendees to find that 91 per cent of them had developed the infection while at the retreat.
The count excluded 24 students who proved through antibody tests that they had already been infected and recovered.
The Center for Disease Control and Prevention reported that an outbreak happened this summer in Wisconsin at a faith-based overnight retreat. They tested 148 students and staff and found 91 per cent of them had developed the infection while at the retreat. The count excluded 24 students who had previously been infected and recovered
CityHealth Urgent Care Medical Assistants Leilany McClure (left) and Aria Alokozai (right) swab two Oakland Airport Fire Rescue employees
Although all retreat attendees were required to wear face masks while traveling to the Wisconsin camp, they were allowed to flout mask suggestions and mingle freely amongst each other.
Some students slept four to six in dormitory rooms, while others slept eight-per-room in yurts. The 21 counselors stayed in similar close quarters in dormitories or yurts.
After the ninth grader's positive diagnosis, he and 11 of his close contacts were quarantined at the camp. All 11 contacts tested negative according to rapid antigen tests and were released from quarantine.
During the first week of camp, however, six of the 11 boys - plus 18 others - said they were experiencing mild symptoms.
Those students were given face masks, but were not placed in isolation from others and continued to unwittingly spread the virus.
Retreat administrators did not conduct contact tracing, making the outbreak that much more potent.
There were no positive diagnoses of attending teachers, who practiced social distancing, wore face masks and quartered separately from students and counselors.
No deaths or hospitalizations were reported in regards to the outbreak.
Now, the CDC has reiterated the importance of mitigation efforts after the school-aged outbreak.
'SARS-CoV-2 can spread rapidly among adolescents and young adults in a congregate setting with inadequate COVID-19 mitigation measures,' officials wrote.
'A robust COVID-19 mitigation plan developed in collaboration with public health authorities is important for preventing and containing similar outbreaks at overnight camps and residential schools.'
Pictured: a CDC graphic shows the dates of symptom onset for cases at the Wisconsin retreat
A medical professional applies a nasal swab during testing at the Orange County Health Services Covid-19 drive-thru site at Barnett Park in Orlando, Florida
The CDC study noted that a silver lining in the outbreak was the potential link between antibodies and coronavirus.
'An important feature of this outbreak was that 24 attendees had documented evidence of antibodies to SARS-CoV-2 before arrival. None of these persons received a positive SARS-CoV-2 RT-PCR test result at the retreat,' the study read.
'These findings provide preliminary evidence that detectable antibodies might provide protection against new SARS-CoV-2 infections for an unknown duration.'
The agency still cautioned that more investigations into the link must be done and, at this time, 'evidence to date is insufficient.'
Wisconsin has recorded the eleventh highest coronavirus case count with 227,000 infections and just more than 2,000 deaths.
The United States has reported more than 8.9million infections and 228,600 deaths since the first outbreak was announced in January.