New study: US colleges experience superspreader events within two weeks of students' return

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  • US colleges and universities that cautiously reopened at the end of 2020 have experienced a new wave of infections 
  • Researchers from Stanford University suggest that although campuses were able to reduce the number of new Covid-19 infections, neighbouring communities were less successful 
  • Mitigating the spread of Covid-19 is dependent on contact tracing, adherence to quarantine periods, flexible transition to online learning and compliance with local regulations

Colleges and universities in the United States continue to experience challenges with reopening their facilities amid the Covid-19 pandemic, with many institutions reporting a new wave of infections after students returned to campus. 

A new study conducted by researchers at Stanford University and published in the journal, Computer Methods in Biomechanics and Biomedical Engineering, revealed that the first two weeks of teaching present a high-risk for campus Covid-19 outbreaks, which spread into surrounding communities. 

The researchers explain that they examined the Covid-19 case reports from 30 publicly available college dashboards across the US during the autumn semester of 2020, which is roughly from September to December. 

The researchers chose 30 institutions who reported their case numbers on a daily basis, those whose cumulative case number was above 100, ten institutions with the highest case numbers nationwide and ten public and private institutions based on national rankings. 

The epidemiology of the Covid-19 outbreak was then modelled according to an SEIR model which includes the susceptible, exposed, infectious and recovered populations which were integrated with Bayesian inference, the study explains. 

Campus outbreaks 

The researchers found that 14 out of the 30 colleges in their study experienced an increase in cases within the first two weeks of class. All campuses conducted regular testing and contact tracing strategies, the researchers note. 

At the peak of these infections, the researchers reveal that over half of the institutions reported 1 000 Covid-19 cases per 100 000 people per week within the first two weeks of returning to campus. 

The researchers’ data also reveals that four institutions reported more than 5 000 cases in total, namely Clemson University, the University of Wisconsin Madison, Brigham Young University, Ohio State University and the University of Florida. 

In 18 out of the 30 institutions, the greatest rise in cases occurred between August and October which was between the second and third waves of Covid-19 nationally, the study explains. 

“This suggests that these initial college outbreaks are unrelated to the national outbreak dynamics. Instead, they are independent local events driven by campus reopening,” according to the researchers. 

Covid-19 outbreaks in surrounding counties

The researchers note that during the first half of the term, the outbreak numbers in the home county closely followed that of 17 campuses under examination. However, during the second half of the term, the counties’ case numbers increased irrespective of the campus dynamics. 

The respective campuses were quick to manage the spread of the virus by implementing a mandatory quarantine period after students returned to campus and conducting regular testing and contact tracing, the study explains. 

“Successful reopening relies on limiting the introduction of the virus during the initial weeks of the term, regular testing and rapid tracing and the collective understanding of the importance of quarantine and isolation,” the researchers conclude.

Image credit: Unsplash

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