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September 24, 2020

When colleges reopened, how many Covid-19 cases resulted? Here's what a new study found.

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    Reopening colleges and universities for in-person instruction has been linked to tens of thousands of additional cases of Covid-19, according to a draft study released Tuesday.

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    Study details

    For the study, which was published preprint on medRxiv and has not yet been peer reviewed, researchers from the University of North Carolina-Greensboro, Indiana University, and the University of Washington and Davidson College examined whether the reopening of 1,400 U.S. colleges and universities affected rates of Covid-19, the disease caused by the new coronavirus, in the surrounding counties.

    To determine the impact, the researchers examined cellphone GPS tracking data, county-level Covid-19 data, and campus reopening schedules from July 15 to Sept. 13, which is before and after students returned to their schools. The researchers focused their study on how colleges and universities implemented classes and not on student behavior.


    The researchers found the reopening of colleges and universities for in-person instruction correlated with an increase in new cases of Covid-19, ranging from a minimum of nearly 1,100 extra cases per day to a maximum of 5,300 extra cases per day. The researchers estimated 3,200 additional Covid-19 cases per day—or 2.4 cases per 100,000 residents a day—as the midpoint range for the projected daily increase in infections.

    The researchers found reopening one university alone for in-person instruction led to an additional 1.7 new cases per day per 100,000 residents in a county. However, the researchers said they found "[n]o such increase … in counties with no colleges, closed colleges or those that opened primarily online."

    According to the Journal, the researchers found a slight uptick in new Covid-19 cases in communities where students moved near their college campuses but took their classes online. When the researchers factored in whether students had traveled from places with high disease incidence rates, they found neighboring counties added 1.2 coronavirus cases per day per 100,000 residents, Kaiser Health News (KHN) reports.

    Ana Bento—an assistant professor of infectious diseases at Indiana University, who co-authored the study—noted that, "[w]hile this study estimates around a 3,000 increase in daily cases, we have to take into account that this is actually likely an underestimate, because we still don't see" people with Covid-19 who are asymptomatic.  


    Some observers applauded the study, but others said it left many unanswered questions.

    For example, the study did not determine whether cases spiked mainly as a result of students catching Covid-19 when they arrived at their campuses or if they were already unknowingly infected upon their return, KHN reports.

    In addition, Jason Christie, a pulmonologist and epidemiologist at the University of Pennsylvania's Perelman School of Medicine, said the study may have missed some of the other underlying factors driving up infections rates, including trends unrelated to the reopening of college and university campuses.

    Bento acknowledged some of the uptick in cases could be potentially attributed to increase in coronavirus testing in counties where students returned to campus for in-person instruction. However, in such an event, Bento said the researchers would have likely seen a quick rise in infections and then either a plateau or decline, instead of an increase two weeks after schools reopened and a continued surge.

    Bento added that it would be "slightly unfair" to assume that cases spiked because students did not follow social distancing guidelines or engaged in other "bad behaviors."

    Bento said, "I think it's more this idea of when you see a huge influx from all over the country, or from different counties, into a college town that we know had a very low burden of Covid throughout the first months, all of a sudden we have this increased probability of infection, because we have a large community of individuals that were susceptible still."

    As colleges and universities prepare for the spring semester, Bento recommended administrators consider a variety of instructional approaches.

    "In order for you to open online, hybrid or meet face to face, there needs to be a different combination of strategies that allows you to catch [cases] early so you're able to control community spread, which is the biggest problem here," Bento said (McAuliff, Kaiser Health News, 9/23; Korn/Abbott, Wall Street Journal, 9/22; Budryk, The Hill, 9/22).

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