OBJECTIVES We evaluated the impact of distancing practices on secondary transmission of severe acute respiratory syndrome coronavirus 2 and the degree of sports-associated secondary transmission across a large diverse cohort of schools during spring 2021. METHODS Participating districts in North Carolina and Wisconsin and North Carolina charter schools offering in-person instruction between March 15, 2021 and June 25, 2021 reported on distancing policies, community- and school-acquired infections, quarantines, and infections associated with school-sponsored sports. We calculated the ratio of school-acquired to community-acquired infection, secondary attack rates, and the proportion of secondary transmission events associated with sports. To estimate the effect of distancing and bus practices on student secondary transmission, we used a quasi-Poisson regression model with the number of primary student cases as the denominator. RESULTS During the study period, 1 102 039 students and staff attended in-person instruction in 100 North Carolina school districts, 13 Wisconsin school districts, and 14 North Carolina charter schools. Students and staff had 7865 primary infections, 386 secondary infections, and 48 313 quarantines. For every 20 community-acquired infections, there was 1 within-school transmission event. Secondary transmissions associated with school sports composed 46% of secondary transmission events in middle and high schools. Relaxed distancing practices (<3 ft, 3 ft) and increased children per bus seat were not associated with increased relative risk of secondary transmission. CONCLUSIONS With universal masking, in-person education was associated with low rates of secondary transmission, even with less stringent distancing and bus practices. Given the rates of sports-associated secondary transmission, additional mitigation may be warranted.

中文翻译：

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K-12 学校中 COVID-19 的二次传播：来自 2 个州的调查结果。

目标 我们评估了 2021 年春季在大量不同学校中保持距离的做法对严重急性呼吸综合征冠状病毒 2 二次传播的影响以及与运动相关的二次传播程度。 方法 北卡罗来纳州、威斯康星州和北卡罗来纳州的参与学区2021年3月15日至2021年6月25日期间提供面对面教学的学校报告了疏远政策、社区和学校获得性感染、隔离以及与学校赞助的体育运动相关的感染。我们计算了学校获得性感染与社区获得性感染的比率、继发感染率以及与运动相关的继发传播事件的比例。为了估计距离和公交车做法对学生二次传播的影响，我们使用了以小学生病例数为分母的准泊松回归模型。结果 在研究期间，1 102 039 名学生和教职员工在 100 个北卡罗来纳州学区、13 个威斯康星州学区和 14 个北卡罗来纳州特许学校参加了现场教学。学生和教职员工有 7865 例原发感染，386 例继发感染，48313 例隔离。每 20 例社区获得性感染，就有 1 例校内传播事件。与学校体育相关的二次传播占初高中二次传播事件的 46%。宽松的距离做法（<3英尺，3英尺）和每个公交车座位上的儿童数量增加与二次传播的相对风险增加无关。结论 在普遍佩戴口罩的情况下，即使在距离和公交车做法不太严格的情况下，面对面教育也与较低的二次传播率相关。考虑到与运动相关的二次传播率，可能需要采取额外的缓解措施。