"The university has pointed to off-campus parties as the main culprit, saying more than 70% of the students who tested positive lived off campus and attended off-campus parties or came into close contact with someone who attended one of the parties."
Link: https://www.southbendtribune.com/news/education/parties-missteps-and-slow-testing-how-notre-dames-covid-19-plan-unraveled/article_30c4f5a6-e26d-11ea-a12a-af1bffb3d946.html