Can Testing Students For Coronavirus Twice A Week Prevent Campus Outbreaks?

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15 Авг 2020, 15:36

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As some campuses welcome students back, administrators are weighing their options to keep the community safe. Some are betting on frequent, regular testing.

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And, why two tests per week? Coronavirus diagnostic tests tend to catch people only during a short window when they’re most infectious. So, a newly infected person may test negative if the sample is taken too early, before the virus has begun to replicate in their body. But, if they’re tested again a few days later, the virus would likely be detected.

«So, by testing frequently the chances of catching that person when their viral load goes up is very high,» Burke says.

Some researchers say it’s time for colleges to embrace testing. «The case for frequency is quite strong now,» says Rochelle Walensky, an infectious disease physician and a professor at Harvard Medical School. «Testing is such a major component of what could be done to get us to a better place on college campuses, and it’s being completely underutilized right now,»she says.

As part of a recent study published in JAMA Network Open, Walensky and her collaborators modeled different scenarios for safely re-opening campuses. They found that simply asking students to report symptoms would not be sufficient.

«We ran thousands of scenarios in our model and we failed to find even one plausible circumstance under which a strategy of simply waiting for symptoms to emerge would be sufficient to contain an outbreak,» says Walensky’s co-author, David Paltiel a professor of public health at Yale School of Medicine.

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The reason: «There’s just so much silent spreading,» Paltiel says. A recent analysis published in PNAS found that silent disease transmission during the presymptomatic and asymptomatic stages are responsible for the majority of cases.

Paltiel and Walensky’s paper concludes that, in conjunction with social distancing and masking, frequent testing of all students might be required to control outbreaks. And they conclude that «low sensitivity» tests which can produce more false negatives are acceptable.

«You can capture a vast majority of the cases in a very short time by repeatedly testing,» Paltiel says. He says resistance to faster, less sensitive tests is a mistake. «The frequency makes up for a world of blemishes with regard to the accuracy of the test,» he says.

Despite the growing call for more testing on campuses, currently, the CDC does not recommend «entry» testing for all returning college students.

Paltiel says this guidance could be dangerous. «It is baffling to me that the CDC has failed to update its guidance, in light of the accumulating evidence that «silent spreaders» are fueling outbreaks,» he says.

The CDC guidance says that entry tests have not been systematically studied.

«A lack of evidence is not the same thing as evidence of a lack of effectiveness,» says physician Aaron Carroll, a professor at Indiana University School of Medicine. «From a public health perspective, every case we identify and isolate is better than not.» He argues entry testing, especially for on-campus students,»combined with a robust program of ongoing, regular testing of as many people as possible, seems like a good idea.»

The CDC’s guidance on campus testing was last updated in late June. Now, as the evidence continues to evolve, a spokesperson for the agency tells NPR they will re-evaluate the guidance in light of the new research. «CDC will incorporate this [JAMA Network Open] study into the body of scientific evidence to date regarding entry testing for college students and will continue to evaluate the guidance,» a spokesperson wrote in an email.

The agency points to many factors to consider including «limited availability of dedicated resources and the logistics needed to conduct broad testing» on campuses.

It’s true that with current testing technology and supply chain shortages, many campuses wouldn’t be able to run frequent tests for all students.

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And the types of rapid saliva tests some colleges have developed are not yet on the market. University of Illinois is currently seeking emergency use authorization from the FDA for its proprietary test, and Yale University is seeking authorization for a very similar test.

Researchers at these institutions say the challenge has been to develop a test that won’t be subject to supply chain snags — and can deliver results faster and cheaper. They say they’ve found a way of working around a time-consuming step in the lab analysis of samples, by using heat to «break open» the virus.

«We get rid of the most cumbersome step,» says Nathan Grubaugh, an assistant professor of epidemiology at Yale School of Medicine. «You lose the most expensive step and the most time-consuming.»

The new technique cuts down significantly the amount of skilled labor required, both in sample collection and lab processing, he says. If approved, these tests could become more widespread fairly quickly, as commercial labs may begin to license them.

Meanwhile, Carroll says his school, Indiana University, is ramping up its surveillance and screening using a combination of saliva tests and antigen tests. «We are testing all on-campus students in all our campuses using antigen testing on arrival,» he explains, and the school is developing plans for ongoing testing.

An antigen test, which can detect proteins from the virus, can pick up active infections and provide results in less than an hour. The FDA says these are reliable if results are positive but negative results «may need to be confirmed with a molecular test.»

And around the country, campuses continue to adjust their testing plans. Harvard University is phasing in new testing protocols: Starting Aug. 16 students living on campus dorms and housing will be tested three times a week. Students living on campus at Brandeis University will be tested two times per week (every three or four days).

By comparison, at the University of Georgia, which typically enrolls about 30,000 undergraduates, asymptomatic testing is voluntary, and the university says it plans to conduct about 300 tests per day.