Can schools be kept open safely even as the COVID-19 pandemic continues largely unchecked? So far the data has been mixed. Studies of spread in schools seem to suggest that they are not a major source of infection. But when countries that closed their schools as part of a package of pandemic restrictions were compared with countries that didn’t, those that closed schools had a lower overall infection rate. So the record on school opening seems a bit mixed.
Yesterday, the CDC released a detailed overview of the spread of SARS-CoV-2 within a single school system in rural Wisconsin. While the results come from a time before the new, more widely distributed species had developed, they show that some of the measures outlined in guidelines for safely reopening schools are working. Thanks to those precautions, infections in school fell by 37 percent compared to infections in the community as a whole, and there were very few infections within the school. But it also raises an obvious question: If these measures work, why don’t we all use them?
The investigation started at the end of August 2020 and continued until the end of November. It focused on the schools of Wood County, Wisconsin, monitoring infections occurring among faculty and staff, and comparing them to the spread of the pandemic in the county as a whole. A total of 4,876 students and 654 employees were included in the data.
The schools have taken many of the steps that experts advised before the start of the school year. Each student was given several mouth caps at the start and wearing a mouth cap was mandatory throughout the period. Compliance with this rule, based on surveys of teachers, was consistently above 90 percent. (However, the report notes that not all educators returned these reports, so there is a chance the data may be missing in the classrooms where compliance was lower.)
Apart from the masks, the schools kept classes small, with 20 students or less. And these student groups were kept together throughout the day, rather than mingling during the day. All students who had COVID-19 symptoms were sent home for isolation, and any siblings they had were similarly kept away from school. The report does not provide information on whether changes to the classrooms – more segregation from students or improved ventilation – are also included in the package of precautions. But overall, these policies are in line with health authorities’ recommendations for safe education.
Out of hand
And the schools were severely tested. As with most of the rest of the United States, COVID-19 cases in the province exploded in the fall. At times, Wood County had a 40 percent positivity rate, meaning four out of every 10 tests for SARS-CoV-2 gave a positive result. This is taken as an indication that there are many more positive cases at the same time that have not been detected.
Overall, the number of cases among the students and staff was significantly lower than in the surrounding community. The rate in surrounding cities in the period was nearly 5,500 cases per 100,000 people. In contrast, the students and staff had a rate of 3,450 cases per 100,000 people. This amounts to a total of 191 cases: 133 among students and 58 among employees.
Contact tracing indicates that only seven of these cases were picked up via school transmission, all of which involved spreading from student to student. All seven of these cases involved spreading between students in the same class group. In fact, three took place within a single class group. The lack of dispersion between class groups is a reassuring confirmation of that strategy.
The main limitation of the analysis is that the testing capacity was clearly not sufficient to track the spread of infections during this study period. There is a good chance that some asymptomatic cases were missed in school during this time, which could influence the conclusions from the contact tracing portion of the experiment. As such, the seven cases assigned to school dispersion should be seen as a lower bound.
There are a few ways to look at this data. The first few are obvious: it is not possible to rule out risks during a pandemic that is out of control. But with the right precautions, it is possible to reduce the risk to students and greatly reduce the chance of picking up new infections at school.
But the main message is that it is impossible to separate the students from the larger community. While infections among college students decreased compared to the wider population, a significant number of college students ended up with SARS-CoV-2, and most of those infections came during interactions that occurred outside of the school system. Which begs the obvious question of whether the wider population would have benefited from adopting more of the practices used by the schools.
With more and more infectious strains rife and vaccine distribution struggling to move forward, it’s critical that we assume everything that can be done in the meantime to limit the spread.