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Yesterday, the Centers for Disease Control and Prevention (CDC) released a detailed report detailing the spread of SARS-CoV-2 in a single school system in rural Wisconsin. Although the results were obtained some time before the evolution of new, more easily spread strains, they show that the guidelines set out some measures on how to safely reopen school work. As a result of these preventive measures, infections in schools have been reduced by 37% compared with infections in the entire community, and infections within schools are rare. But this also raises an obvious question: if these measures are effective, why have we not used them?
The research started at the end of August 2020 and continued until the end of November. It focuses on schools in Wood County, Wisconsin, tracking the infection among its staff and comparing it with the spread of the disease throughout the county. Overall, the data includes 4,876 students and 654 staff.
Before the start of the school year, the school took many steps suggested by experts. Each student will receive multiple masks at the beginning of their studies and must use masks during this period. According to a survey of teachers, the compliance rate for this rule is always higher than 90%. (However, the report does point out that not all teachers have returned these reports, so it is possible that data is missing from classrooms with lower compliance rates.)
In addition to masks, the school also maintains small classes with no more than 20 students in each class. These student groups stay together all day, not mixed together all day. Any student with symptoms of COVID-19 was sent home for quarantine, and any siblings they had were prohibited from attending school. The report did not contain any information about classroom changes (increased student spacing or improved ventilation), nor was it included in the package of preventive measures taken. But overall, these policies are in line with health authorities’ recommendations on safe schooling.
out of control
And the school was severely tested. As in most other parts of the United States, COVID-19 cases in this county broke out in the fall. Sometimes the positive rate in Wood County is 40%, which means that 4 out of 10 SARS-CoV-2 tests are positive. This means that no more positive cases have been detected at the same time.
In general, the number of cases among students, faculty and staff is much lower than the surrounding communities. During this period, the incidence in surrounding towns was about 5,500 cases per 100,000 people. In contrast, the incidence of students and faculty members is 3,450 cases per 100,000 people. This means 191 cases in total: 133 for students and 58 for staff.
Contact tracing showed that only 7 of these cases were acquired through school transmission, and all cases involved transmission between students. All seven cases involved students in the same classroom group. In fact, three of them occurred in a single classroom group. The lack of communication between classroom groups is a reassuring test of this strategy.
The biggest limitation of the analysis is that during this study period, the testing capacity was obviously not enough to keep up with the spread of infection. During this period, it is very likely that some asymptomatic cases were missed in the school, which may affect the conclusion of the contact tracing part of the experiment. Therefore, the seven cases allocated for school dissemination should be considered as the lower limit.
There are several ways to view this data. The first few are obvious: eliminating risks in an out-of-control pandemic is not impossible. However, if appropriate precautions are taken, it is possible to limit the risk to students and severely limit the chance of contracting new viruses in schools.
But the key message is that it is impossible to separate students from the larger community. Although the infection rate among students has declined relative to the wider population, a large number of students have been infected with SARS-CoV-2, and most of these infections come from interactions outside the school system. This raises the obvious question of whether the wider population will benefit from adopting more practices adopted by schools.
As more infectious strains become more common and the distribution of vaccines is striving to succeed, it is vital that we take all feasible measures to limit its spread.