Reopening college and university campuses for in-person classes during late summer this year could be associated with more than 3,000 additional cases of COVID-19 per day in the United States in recent weeks, according to a new study.

The findings call into question the practicality of face-to-face classes during the COVID-19 pandemic, and are important as colleges and universities plan their spring 2020 semesters, said researchers from the University of North Carolina at Greensboro, Indiana University, the University of Washington and Davidson College.

The findings are yet to be peer reviewed and have not yet been published online.

To track COVID-19 cases and study their association with students attending classes at college campuses, the team used location data from a database of cellphone users who agreed to share information. The information was gathered from July 15 to September 13.

They also looked at COVID-19 infection rates in counties with campuses, before and after colleges reopened and students arrived.

The researchers noted significant increases in counties where colleges had reopened for face-to-face instruction, especially in and around campuses with students who came from areas with higher incidences of COVID-19.

"We are able to predict between 1,000 and 5,000 additional cases a day due to colleges reopening for face-to-face instruction, with our best estimate being somewhere around 3,219 cases a day," said Ana Bento, a co-author of the study from Indiana University's School of Public Health.

The study did not go into how many COVID-19 cases were "imported" – or from students who arrived on campuses – and how many were local transmissions.

The team also pointed out that asymptomatic cases may not have been caught unless testing was done on campuses regardless of symptoms, and that the study did not look at measures taken by individual colleges.