Testing and Preventing Outbreaks
Testing for COVID-19
The “T” in “VITAL” stands for both Testing and Transparency. Persons with asymptomatic and presymptomatic infection are responsible for at least 50% of transmission of COVID-19.
An expanded surveillance testing strategy is critical to rapidly identify people without symptoms. A weekly screening regimen can reduce in-school infections, and increase confidence in safety for staff and families.
Together, we can prevent the spread of COVID-19, with the use of testing!
What needs to be done now?
The new CDC guidance to schools is that we should have an effective testing plan in place ASAP, prior to returning more students to school buildings. It actually probably should already be in place, based on the guidance.
We want APS to:
- Develop an adequate testing plan to include location, test administrators, criterion, random sampling percentages (per current CDC guidance based on severity) for asymptomatic rapid antigen testing (for real-time results as opposed to send out PCR results).
- Consider cost-effective, advance warning wastewater COVID testing for all schools — and then an asymptomatic testing schedule that includes 10-20% of staff and students weekly where wastewater indicates there are positive cases.
- Create a case dashboard to disclose in real time positive cases, broken out by school/location, similar to what FCPS and other districts have done. Report out separately for ALL positive cases based on school site, in-school cohort (class), and/or athletic team. Do not lump them all together.
- Create a clear quarantine and notification policy, which lays out who must quarantine, for how long, and under what circumstances.
- Obtain consent, community support, and engagement for the testing plan.
- Implement expanded screening testing in a manner that promotes health equity for persons with limited resources or other barriers to accessing health care.
Testing Best Practices:
Combination of Wastewater and Rapid Antigen Testing
RAPID TESTING: If only rapid antigen testing is used for surveillance testing (without wastewater testing), 20% of staff and students should be tested weekly. If regional transmission is in the CDC-defined “red” category, twice-weekly rapid antigen testing for 10-20% of staff and students should be administered.
False positives and false negatives should be double-checked with a second test. When a rapid test is negative in the presence of COVID symptoms, a PCR test should be used to confirm. When a rapid test is positive in the absence of symptoms, a PCR test should also be used to confirm.
Rapid antigen testing can also be used for all staff AND students who have had a known exposure through contact tracing of class, lunch, and recess cohorts.
Rapid antigen surveillance testing costs more than wastewater surveillance testing if it is the only type of test used, and APS would need to test about 20% of people per school per week to effectively catch outbreaks, and it is less effective at catching asymptomatic carriers than wastewater testing. This is less cost-effective and useful when used alone compared to when used in targeted conjunction with wastewater testing.
Some school districts (Colorado, etc.) and companies (like Amazon) are using an at-home testing option for staff and older students 15+, called the Abbott BinaxNOW rapid antigen test card, which can give results at home and be used with an app for reporting. Students ages 4-14 need adult assistance. It uses a less-invasive nasal swab and produces results within 15 minutes on a card which shows either 1 line (-) or 2 lines (+), similar to an at-home pregnancy test.
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WASTEWATER TESTING: This might be the most cost-effective approach to know immediately if a school has COVID-19 cases, and can also be used with more expensive antigen testing to follow up and search for spread within a school community.
The University of Arizona, UVA, and other universities have used this method to target specific dormitories for individual follow-up testing to stem spread from asymptomatic and presymptomatic cases. Maryland tests the wastewater in public housing and corrections facilities. Omaha Public Schools uses this, too. Municipalities across the United States have implemented programs to provide real-time warnings of COVID-19 spikes in their communities.
“Wastewater data provided a lead time of eight to nine days for changes in SARS-CoV-2 viral levels compared to confirmed case counts or proxy indicators,” according to Mathematica research in North Carolina.
Weekly wastewater surveillance testing is a highly effective and less expensive surveillance testing alternative to swab-based tests (PCR, rapid antigen).
Wastewater testing is more sensitive to pre-symptomatic cases than rapid antigen testing. A negative rapid antigen test does not rule out COVID-19 before symptoms arise, but can be useful when a test is positive. This type of testing has a faster turn-around than PCR testing, but requires infrastructure. This type of test must be processed within 15 minutes of administration or the test is invalid.
Locally, Microbac Laboratories would charge about $280 per school to test on a weekly basis. If a school has positive cases, the school site could be reverted to virtual until individuals could be tested to determine the source and contact trace from that point prior to return. This is compared to $5 per rapid antigen test as well as overhead costs of personnel. Waste testing does not require consent or additional personnel to administer monitoring.
We have also written to Arlington County about implementing a countywide wastewater alert program to provide real-time information that isn’t dependent on people’s access to and choice to get tested.
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In conjunction with wastewater surveillance, rapid antigen testing for a statistically relevant percentage of staff AND students at locations where wastewater has identified positive cases should be done.
Programs with opt-outs are less effective than programs where all, or as close to all as possible, are included.
Research and Resources:
Symptoms of COVID-19 – Evaluating a Child – VDH Algorithm
Impactful Testing Programs and Options
Building the Evidence for Reopening Schools: Regular Covid-19 testing in primary and secondary educational settings is critical to getting students and teachers back to in-person instruction. The reports include early results from six K-12 testing pilots.