Investigation of a SARS-CoV-2 outbreak in a Texas summer camp resulting from a single introduction

SARS-CoV-2 is the etiological agent responsible for the COVID-19 pandemic. It is estimated that only 10 aerosol-borne virus particles are sufficient to establish a secondary infection with SARS-CoV-2. However, the dispersal pattern of SARS-CoV-2 is highly variable and only 10– 20% of cases are responsible for up 80% of secondary infections. The heterogeneous nature of SARS-CoV-2 transmission suggests that super-spreader events play an important role in viral transmission. Super-spreader events occur when a single person is responsible for an unusually high number of secondary infections due to a combination of biological, environmental, and/or behavioral factors. While super-spreader events have been identified as a significant factor driving SARS-CoV-2 transmission, epidemiologic studies have consistently shown that education settings do not play a major role in community transmission. However, an outbreak of SARS-CoV-2 was recently reported among 186 children (aged 10-17) and adults (aged 18 +) after attending an overnight summer camp in Texas in June 2021. To understand the transmission dynamics of the outbreak, RNA was isolated from 36 nasopharyngeal swabs collected from patients that attended the camp and 19 control patients with no known connection to the outbreak. Genome sequencing on the Oxford Nanopore platform was performed using the ARTIC approaches for library preparation and bioinformatic analysis. SARS-CoV-2 amplicons were produced from all RNA samples and >70% of the viral genome was successfully reconstructed with >10X coverage for 46 samples. Phylogenetic methods were used to estimate the transmission history and suggested that the outbreak was the result of a single introduction. We also found evidence for secondary transmission from campers to the community. Together, these findings demonstrate that super-spreader events may occur during large gatherings of children.