Many kindergarten through grade 12 (K-12) schools offering in-person learning have adopted strategies to limit the spread of SARS-CoV-2, the virus that causes COVID-19 (1). These measures include mandating use of face masks, physical distancing in classrooms, increasing ventilation with outdoor air, identification of close contacts,* and following CDC isolation and quarantine guidance† (2). A 2-week pilot investigation was conducted to investigate occurrences of SARS-CoV-2 secondary transmission in K-12 schools in the city of Springfield, Missouri, and in St. Louis County, Missouri, during December 7-18, 2020. Schools in both locations implemented COVID-19 mitigation strategies; however, Springfield implemented a modified quarantine policy permitting student close contacts aged ≤18 years who had school-associated contact with a person with COVID-19 and met masking requirements during their exposure to continue in-person learning.§ Participating students, teachers, and staff members with COVID-19 (37) from 22 schools and their school-based close contacts (contacts) (156) were interviewed, and contacts were offered SARS-CoV-2 testing. Among 102 school-based contacts who received testing, two (2%) had positive test results indicating probable school-based SARS-CoV-2 secondary transmission. Both contacts were in Springfield and did not meet criteria to participate in the modified quarantine. In Springfield, 42 student contacts were permitted to continue in-person learning under the modified quarantine; among the 30 who were interviewed, 21 were tested, and none received a positive test result. Despite high community transmission, SARS-CoV-2 transmission in schools implementing COVID-19 mitigation strategies was lower than that in the community. Until additional data are available, K-12 schools should continue implementing CDC-recommended mitigation measures (2) and follow CDC isolation and quarantine guidance to minimize secondary transmission in schools offering in-person learning.

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2020年12月，密苏里州圣路易斯县和斯普林菲尔德市通过实施缓解策略的12年级学校对SARS-CoV-2二级传播进行了试点调查。

许多提供亲自学习的幼儿园到12年级（K-12）学校都采用了限制SARS-CoV-2传播的策略，SARS-CoV-2是导致COVID-19的病毒（1）。这些措施包括强制使用口罩，在教室中进行物理疏散，增加室外空气的通风，确定近距离接触*，以及遵循CDC隔离和检疫指南†（2）。进行了为期2周的初步调查，以调查2020年12月7日至18日在密苏里州斯普林菲尔德市和密苏里州圣路易斯县的K-12学校发生SARS-CoV-2二次传播的情况。在两个地方都实施了COVID-19缓解策略；然而，斯普林菲尔德实施了一项修改后的隔离政策，允许18岁以下的近距离接触者与与COVID-19的人有学校联系并在接触过程中符合遮蔽要求的人继续进行面对面的学习.§参与的学生，老师和工作人员与来自22所学校的COVID-19（37）进行了访谈，并与他们在校内的密切联系人（联系人）（156）进行了访谈，并为联系人提供了SARS-CoV-2测试。在接受测试的102个校本接触者中，有两个（2％）的测试结果呈阳性，表明可能是校本SARS-CoV-2二次传播。两位联系人都在斯普林菲尔德，并且不符合参与修改后的隔离的条件。在斯普林菲尔德，根据修改后的隔离规定，允许42名学生联系者继续进行面对面的学习；在接受采访的30位受访者中，有21位接受了测试，没有一个得到正面的测试结果。尽管社区传播率很高，但实施COVID-19缓解策略的学校中的SARS-CoV-2传播率低于社区。在可获得更多数据之前，K-12学校应继续实施CDC建议的缓解措施（2），并遵循CDC隔离和隔离指南，以最大程度地减少提供亲自学习的学校中的二次传播。