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Most elementary school-associated COVID-19 cases in one suburban Atlanta district involved teachers somewhere in the transmission chain, CDC researchers found.

With nine clusters of epidemiologically linked COVID cases in eight Cobb County elementary schools totalling 63 cases, eight of the clusters included at least one teacher, reported Snigdha Vallabhaneni, MD, of the CDC, and colleagues in an early edition of the

The ninth cluster accounted for just six of the cases. In all, 13 teachers, 32 students, and 18 of their household contacts tested positive, the group reported. The smallest cluster had three cases and the biggest had 16.

Who triggered the clusters, however, was often less clear. An educator was identified as the index patient in four clusters; in one cluster it was a student; and in the remaining four clusters, the researchers couldn't tell.

Eight clusters involved at least one educator and educator-to-student transmission, four involved probable student-to-student transmission and three involved probable student-to-educator transmission. Because educators are more likely to have symptoms, they were more likely to be tested, "possibly resulting in missed instances of student-to-student and student-to-educator transmission," Vallabhaneni and colleagues wrote.

The report did not indicate illness severity for the individuals who tested positive for SARS-CoV-2 infection; thus, it shed no light on the clinical significance of these school-based COVID cases.

Vallabhaneni and colleagues did, however, suggest that mitigation measures in the schools were less than optimal: the recommended 6 feet of distancing was not maintained in any of the nine clusters and, in five, students' mask usage was "inadequate."

CDC recently released guidance for returning to in-person education, as a substantial proportion of U.S. K-12 schools have been remote, due to the COVID-19 pandemic. In the guidance, CDC officials stressed the lack of evidence for in-school transmission, while emphasizing the importance of mitigation measures, such as physical distancing, mask wearing and hand hygiene.

In this study, researchers examined data from eight public elementary schools comprised of approximately 2,600 students and 700 staff members in Georgia from Dec. 1, 2020 to Jan. 22, 2021. Students and staff attended in-person education for 24 in-person school days. They noted community transmission in this area (7-day average cases per 100,000 persons) increased by 300%, from 152 to 577 cases during this time.

While RT-PCR testing was offered free of charge to all contacts who were exposed in school, within 5-10 days of their last documented in-school exposure, 40% of contacts refused testing or could not be reached. Clusters were defined as "epidemiologic links between an index patient and two or more persons who likely acquired SARS-CoV-2 infection in school." Cases were excluded if transmission was determined to likely occur outside school.

The two clusters with educator-to-educator transmission likely occurred during in-person meetings or staff lunches, Vallabhaneni and colleagues suggested, and educator-to-student transmission probably occurred in the classroom.

They implicated "small group instruction" in seven of nine clusters, where educators worked "in close proximity to students," and inadequate mask use by student in five clusters, as students were allowed to eat lunch in their classrooms, "which may have facilitated spread."

"Messaging to improve awareness among educators about the risk for acquiring SARS-CoV-2 infections from colleagues in addition to students is needed," the authors wrote, noting the school district already implemented "administrative changes to prevent nonessential in-person interactions among educators."

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