Study investigates SARS-CoV-2 outbreak in children and adults after attending overnight summer camp
In a recent report published on the medRxiv*preprint server, researchers investigated an outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in people who attended an overnight summer camp in Texas in June 2021.
The dispersal dynamics of SARS-CoV-2 are highly variable, with the majority of COVID-19 patients not transmitting SARS-CoV-2 and only a few patients with coronavirus disease 2019 (COVID-19) being responsible for secondary SARS-COV-2 infections. The heterogeneous transmission of SARS-CoV-2 indicates that super-diffusers play an essential role in the transmission of SARS-CoV-2.
Superspreader events occur when an infected individual is responsible for an increase in secondary infections. Studies have consistently reported that educational settings do not contribute to community transmission of SARS-CoV-2. On the contrary, the SARS-CoV-2 outbreak in Texas recently occurred among 186 children and adults who attended an overnight summer camp in Texas in June 2021.
The Texas epidemic
The SARS-CoV-2 outbreak occurred among overnight camp attendees in June 2021 at the start of the Delta variant wave in the United States (US), when cases were still low in the community but were growing rapidly.
A total of 451 people attended the camp, including 364 children (under the age of 18) and 87 adults (over the age of 18). After the end of the camp, 186 participants developed SARS-CoV-2 infections confirmed by reverse transcription-polymerase chain reaction (RT-PCR).
Of the participants, 6% and 19% and 6% were partially vaccinated and fully vaccinated, respectively. Pre-arrival RT-PCR test reports were not required to attend the camp, and no post-arrival RT-PCR testing was performed. A primary attack rate of 41% was observed among camp participants, of whom 20% and 48% were vaccinated and unvaccinated, respectively.
Ribonucleic acid (RNA) was isolated from 55 nasopharyngeal swabs obtained from SARS-CoV-2 infected camp attendees (n=36) and community members (n=19) and subjected to sequencing of the Oxford Nanopore genome using the ARTIC approach. Subsequently, libraries were prepared and bioinformatics analysis was performed. Additionally, 4085 complete genomes published in the Global Initiative on Sharing All Influence Data (GISAID) database were collected from Harris County and Galveston County, Texas, and compared phylogenetically to genomes collected from camp participants using the Nextstrain platform.
SARS-CoV-2 amplicons were produced from RNA of all patients, and 70% of the SARS-CoV-2 genome was successfully reconstructed with >10X coverage from 44 samples (13 Galveston County residents and 31 camp attendees). The results match three genomes isolated from Arlington family members who tested positive for SARS-CoV-2 in contact with asymptomatic campers after camp ended.
The evolution of the SARS-CoV-2 genome was determined using IQ-Tree phylogenetic analysis, which showed that all SARS-CoV-2 genomes obtained from camp participants and the Arlington family shared a common ancestor. This indicated the start of the SARS-CoV-2 outbreak from a SARS-CoV-2 positive camp attendee.
Additionally, SARS-CoV-2 genomes obtained from camp attendees who shared risk factors such as common cabins or buses did not demonstrate clustering. Similarly, SARS-CoV-2 genomes obtained from siblings in the family did not cluster, indicating that SARS-CoV-2 transmission occurred during summer camp. Interestingly, several SARS-CoV-2 genomes obtained from individuals who were not camp attendees clustered with camp attendees, indicating that SARS-CoV-2 was transmitted from camp attendees to the community.
Phylogenetic analysis from the Nextstrain platform detected 29 genomes that demonstrated clustering with the genomes of camp participants obtained after the end of the summer camp, i.e. between June 28, 2021 and July 30 2021. This indicated that community transmission of SARS-CoV-2 was from the camp and through July 30, 2021.
Overall, the study results showed that superspreading of SARS-CoV-2 can occur at large educational gatherings. The Texas outbreak most likely resulted from a single SARS-CoV-2 positive camp attendee who transmitted SARS-CoV-2 to other campers and subsequently to community residents. This led to a chain of SARS-CoV-2 transmission that persisted until at least the end of July 2021.
The study highlights the risks of contracting SARS-CoV-2 infections in overnight summer camps that do not incorporate COVID-19 prevention strategies such as vaccination and HIV testing. SARS-CoV-2 before and after camp attendees arrive. Furthermore, the authors believe that the present work is the first of its kind to integrate epidemiological, phylogenetic and genomic approaches to investigate a SARS-CoV-2 outbreak occurring in a summer camp overnight.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be considered conclusive, guide clinical practice/health-related behaviors, or treated as established information.