Regular rapid testing detects COVID-19 soon enough to stop transmission
in schools
Researchers use mathematical model to simulate COVID-19's spread in the classroom

Date:
July 8, 2021
Source:
Simon Fraser University
Summary:
Proactive, frequent rapid testing of all students for COVID-19 is
more effective at preventing large transmission clusters in schools
than measures that are only initiated when someone develops symptoms
and then tests positive, researchers have found.



FULL STORY ========================================================================== Proactive, frequent rapid testing of all students for COVID-19 is more effective at preventing large transmission clusters in schools than
measures that are only initiated when someone develops symptoms and then
tests positive, Simon Fraser University researchers have found. Professors Caroline Colijn and Paul Tupper used a mathematical model to simulate COVID-19's spread in the classroom and published their research results
today in the journal PLOS Computational Biology.


==========================================================================
The simulations showed that, in a classroom with 25 students, anywhere
from zero to 20 students might be infected after exposure, depending on
even small adjustments to transmission rates for infected individuals
or environments.

"When schools have reopened during the COVID-19 pandemic, in some places
there have been large clusters of infections, and in others very little transmission," says Colijn, SFU mathematics professor and Canada 150
Research Chair in Mathematics for Evolution, Infection and Public
Health. "In our simulations, we explored what factors affect cluster
size, and what interventions can be used to prevent large clusters."
The researchers tested the effectiveness of two different transmission
control strategies.

In the first, when a student (or teacher/staff member) develops symptoms,
they are told to stay home, tested using a PCR test, and if the test
result is positive, control measures are introduced in the classroom,
such as telling the infected individual's close contacts to stay home.

In the second strategy, all students in the class are tested using
rapid tests on a regular basis, whether they have symptoms or not. When
a student tests positive, there is an intervention to prevent further transmission.



==========================================================================
The researchers found that in scenarios with high transmission rates, interventions used in the first control strategy, where preventive
actions took effect after a positive test result, were too slow to
prevent large outbreaks.

Using rapid tests to screen the whole population and catch infections
before symptoms developed, as in the second strategy, led to preventing
large outbreaks.

"We found that interventions that only took effect after someone developed symptoms and tested positive were too slow to prevent large clusters;
only regular monitoring of asymptomatic individuals could prevent the
worst outcomes," says Colijn.

Their study is timely as B.C. is expected to enter Step 4 of its reopening
in September and concerns remain about a resurgence of COVID-19 in
the fall.

Regular screening for COVID-19 in the form of rapid testing has not been
widely used in B.C. schools, though Alberta and Saskatchewan have plans
to deploy rapid testing in schools in the fall, and Nova Scotia has long embraced rapid testing in a variety of settings.

Tupper says they hope to use data on transmission and cluster sizes in
schools to estimate key unknowns about COVID-19 in schools, such as the
rate of transmission, and how much it varies from classroom to classroom.

"We could then see how transmission depends on preventative measures
that are put in place, such as mask use, improved ventilation and hand washing," he says. "This would inform which interventions, after a case
is detected, would be the most effective." The research results could
be applied to other settings in which people spend multiple hours per
day with the same group of approximately 20-30 others.

"Our results were based on simulations of a classroom, but the same considerations apply to other settings such as workplaces, or communal
living settings such as long-term care homes," says Tupper, noting that
their previous work points to the effectiveness of regular rapid testing
in protecting residents of long-term care homes.

Tupper's research was supported by an NSERC (Canada) Discovery
Grant. Colijn was supported by a Genome BC grant (COV142) and by
the Canada 150 Research Chairs program of the Federal Government of
Canada. The researchers also thank Covid E'coles Que'bec for the data
on cluster sizes in Que'bec schools.

========================================================================== Story Source: Materials provided by Simon_Fraser_University. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Paul Tupper, Caroline Colijn. COVID-19 in schools: Mitigating
classroom
clusters in the context of variable transmission. PLOS Computational
Biology, 2021; 17 (7): e1009120 DOI: 10.1371/journal.pcbi.1009120 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/07/210708143931.htm

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