Mitigation, not testing, key to keeping schools safe

Ginny Gnadt’s May 25 opinion column blames the COVID-19 woes of the city of Chesapeake on schools; but a close inspection of the data reveals otherwise. In fact, you could say schools were an effective mitigation strategy. Allow me to explain.

It’s important to note that it’s invalid to compare the total number of COVID-19 cases in the Virginia Beach and Chesapeake school systems for a couple of reasons. First, the amount of on-campus time was dramatically different for the two cities. Chesapeake only had one virtual period since mid-September, while other local school districts have attended virtually.

Cases coming into schools and transmission occurring within the school are two separate concepts. Chesapeake schools saw cases because they remained open: Kids learned safely in person despite high community transmission.

When examining publicly available data presented by both divisions, a clear comparison cannot be made. In Chesapeake, the total number of on-campus cases among students and staff is 1,267 (350 over the winter virtual time). While in Virginia Beach, the total number of on-campus cases reported is 708. The methodology varies between districts, counts are more approximate than exact and are taken out of context in Gnadt’s assessment.

What is important, and can’t be found on the websites, is that 70% of the cases in Chesapeake were community or household acquired and 63% of cases occurred in the first semester when community transmission was at an all-time high. Approximately half of those cases occurred during the virtual period.

Powerful, strict, aggressive mitigation protects students and staff, so Chesapeake schools maintained those policies. The school epidemiologist and health services worked tirelessly on contact tracing, investigation and quarantining 4,461 exposed persons which broke possible transmission chains.

And it worked. There were only 48 in-school transmissions: 60% (29) staffto-staff, 17% (8) staff-to-student, 19% (9) student-to-student and 4% (2) studentto-staff. Mitigation works.

The next issue is the use of in-school testing. To my knowledge, no evaluation of testing has taken place in the absence of concurrent mitigation strategies, for obvious ethical reasons, so it is difficult to delineate the true impact of testing by itself. In New York City, where more than 234,000 asymptomatic students and staff across approximately 1,600 schools were tested last fall, the positivity rate from screening was 0.4%.

If asymptomatic spread was happening in schools, you would expect to see multiple outbreaks and clusters. That has not been the case in Chesapeake.

Testing can be divided into two categories — diagnostic to determine the presence or absence of disease or screening which is primarily for early detection and containment in populations with a high risk of transmission. Diagnostic testing is readily available in our community. This testing is highly recommended for people who are symptomatic or close contacts.

Screening in populations where the transmission risk is low, as indicated in the above discussion on the Chesapeake schools, can statistically result in high false positives leading to unnecessary isolation and quarantine. We have to be careful to avoid conflating a negative test with safety due to the long incubation period.

The key to avoid transmission is layered mitigation — masks, distancing, isolation and quarantine, improved ventilation, hand hygiene and vaccination. Testing is most beneficial and valid when used on a day of activities when mitigation is difficult to maintain, such as close-contact sports.

When targeted and based on knowledge of how to interpret, screening has its place; however, it can be deceptive if applied beyond the day of screening. Studies into the effectiveness and implications of screening in schools are ongoing.

It is simply premature to commit the entire district to testing at this time, especially when mitigation is proven effective. Chesapeake uses evidence-based practices and will continue to take every measure to protect staff and students.

In closing, I’d like to commend the knowledgeable Chesapeake school team whose work has permitted students to attend in-person.