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A new study on Duke University’s coronavirus screening and surveillance strategy released Tuesday in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report emphasizes the importance of generalized testing of asymptomatic individuals to prevent transmission and provides support for the feasibility of a pooled testing approach, in which multiple samples are combined into a single test.
The Duke study adds to the evidence for frequent mass testing of all students on campus. A study published last summer by researchers at Harvard and Yale universities JAMA network open also argued for the need for frequent surveillance testing of asymptomatic students in order to prevent epidemics on campuses. But it was a modeling study of a hypothetical cohort of students, while Duke’s is based on real-world campus test data this fall.
In the first 10 weeks of the fall semester, Duke completed 68,913 tests on 10,265 students. Just over half (51%) of the total 84 students who tested positive were asymptomatic – a finding that suggests, as the article states, “that a substantial proportion of infections would be missed with only symptomatic tests.
“Some of these people had a very high viral load: this translates into the amount of virus they had when we tested them,” said Thomas Denny, lead author of the article, professor of medicine at Duke University. School of Medicine. and COO at the Duke Human Vaccine Institute. “They are asymptomatic, they don’t know they are infected and they have a very high viral load. If these people walk around dormitories or classrooms, this is where you run the risk of seeding many infections. “
A recent analysis from the College Crisis Initiative at Davidson College in North Carolina found that only a quarter of colleges conduct regular mass screening or surveillance tests of students this fall, and only 6% routinely test all students. The majority of colleges either did not have a clear test plan or only test students who are symptomatic or have been exposed to COVID-19.
Denny and his co-authors argue that their findings “underscore the importance of combined screening and contact tracing strategies beyond symptomatic testing, in combination with other preventive measures.” Overall, the article argues that Duke’s frequent surveillance testing program combined with harm reduction measures “likely contributed to a prolonged period of low transmission on campus.”
Duke’s screening strategy included mandatory entrance testing of students upon their return to campus this fall, frequent common asymptomatic screening of students, and testing for symptomatic and exposed students, combined with contact tracing measures and quarantine. Since September 20, the university has tested residential undergraduates twice a week, off-campus undergraduates once or twice a week, and graduate students about once a week.
For his surveillance screening, Duke grouped specimens of five different students into one combined sample for testing. Positive pools were marked for “deconvolution”, or further testing of each of the five individual samples.
The article argues that pooling samples “can allow for large-scale testing while minimizing required resources.”
“For pooled tests, the time between sampling, return of a positive pool, subsequent deconvolution and return of clinical results was 18 to 30 hours,” the authors write. “In addition, pooled testing has saved nearly 80% in reagent use and lab resources compared to testing each individual sample.”
Of the 84 students who tested positive, nine cases were detected using entry testing, 29 cases were identified through asymptomatic pooled testing and 23 through contact tracing.
“So the combined number of asymptomatic student cases identified by testing (entry and pooling) and cases among all students identified by contact tracing accounted for 61 (73%) of the 84 COVID-19 cases that might not have been detected so quickly. or completely through symptomatic testing alone, ”the article states.
Also of note, the authors wrote that contact tracing found no evidence to link the transmission to the in-person classes.
The authors also found that students’ test compliance by the scheduled test date was around 95%. Students who missed scheduled test appointments did not have access to campus facilities and services.
In addition to testing, contact tracing, and quarantine, other measures Duke took to mitigate risk included converting dorms to single occupancy, modifying classrooms and common areas for distancing social and the distribution of packaged meals. All of the students signed a behavioral pact agreeing to comply with mandatory facial masking and social distancing requirements and to participate in entrance and surveillance tests.
“The success of this is really the success of a great collaborative team at Duke with incredible institutional support behind it,” said Denny. “These things don’t happen if you can’t put together a team and have the institutional support to make it happen.”
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