Can schools be safely kept open because the COVID-19 epidemic is largely uncontrolled? So far, the data has been mixed. Studies of prevalence in schools suggest that they are not a major source of infection. But when countries closed their schools as part of a package of epidemic restrictions, they were not compared to those whose schools were closed, with lower rates of infection. Therefore, the school opening record is slightly mixed.
Yesterday, the CDC released a detailed look at the spread of SARS-CoV-2 within the single school system in rural Wisconsin. While the results came a while before the new, more easily spread strains developed, they reveal some of the measures in the guidelines on how schools should work safely. Thanks to those precautions, school infections were reduced by 37 percent compared to infections in the community at large, and there were very few infections within the school. But it also raises an obvious question: if these measures work, why aren’t we all using them?
The study began in late August 2020 and continued until late November. It focused on schools in Wood County, Wisconsin and tracked the transition between its faculty and staff as well as compared those to the spread of the epidemic in the county. In total, 4,876 students and 654 staff members were included in the data.
The schools took several steps, which experts were advising before the start of the school year. Several face masks were provided to each student when they started, and the use of masks was mandatory throughout. Based on the survey of teachers, compliance with this rule was consistently above 90 percent. (However, the report does note, that not all teachers have returned these reports, so there is a chance that the data is missing those classrooms – this compliance was low.)
In addition to masks, schools put class sizes at 20 students or less. And these student groups were kept together during the whole day, rather than during day time. Any students who had COVID-19 symptoms were sent home for separation, and any of their siblings were barred from going to school. There is no information in the report as to whether changes in classrooms — increased student isolation or improved ventilation — were also included in the package of precautions to be taken. But overall, these policies are in line with health officials’ recommendations for safe schooling.
Out of control
And the schools were put to a serious test. Like the rest of the United States, COVID-19 cases in the county exploded in the autumn. At times, Wood County’s positivity was 40 percent, meaning that four out of every 10 tests for SARS-CoV-2 produced positive results. This is taken as an indication that there are far more positive cases at the same time that have not been detected.
Overall, the case between students and staff was significantly lower than the surrounding community. During this period the rate was around 5,500 cases per 100,000 people in the surrounding cities. In contrast, the rate of students and staff was 3,450 cases per 100,000 people. This translates to a total of 191 cases: 133 among students and 58 among staff members.
Contact tracing indicated that only seven of these cases were picked up via transmission to the school, all of which involved student-to-student spreads. All seven of these cases spread among students in the same class group. In fact, three of them occurred within the single class group. The lack of diffusion among class groups assures validation of that strategy.
The biggest limitation of the analysis is that the test potential was apparently not sufficient to keep up with the spread of infection during this study period. There is a very good chance that some asymptomatic cases were left in the school during this period, which may have influenced the findings from the contact tracing part of the experiment. As such, the seven cases assigned to in-school dissemination should be viewed as lower limits.
There are a few ways to view this data. The first few are clear: it is not impossible to eliminate risk during an out-of-control epidemic. But, with proper precautions, it is possible for students to limit the risk and severely limit the possibility of taking new infections at school.
But the main message is that it is impossible to separate students from the larger community. While infection among students was down relative to the broader population, a significant number of students were injured with SARS-COV-2, and most of those infections occurred during interactions outside the school system. Which raises the obvious question of whether the wider population would benefit from greater adoption of practices used by schools.
With the widespread and vaccinated distribution of more infectious strains struggling to move forward, it is important that we adopt anything that can meanwhile be done to limit the spread.