Only four people tested positive for coronavirus last week at the University of Idaho, down from 24 positive cases a week ago.

However, the percentage of positive tests increased during that time.

Here’s what happened: Before classes began on Aug. 24, the U of I screened thousands of students and staff. Last week, with the fall semester under way, the U of I shifted to “surveillance testing,” and testing students who have been under quarantine for at least six days.

As a result, the U of I ran only 205 tests last week. Even so, less than 2 percent of cases came back positive — well below the 5 percent positivity rate that the World Health Organization considers a pivotal threshold.

As previously reported, Boise State University counted 32 coronavirus cases last week, up from eight cases the previous week. Twenty-seven cases involved students off campus, two cases involved students living on campus, and three cases involved faculty or staff.

In its most recent report, Idaho State University reported nine coronavirus cases for the seven-day period ending Sept. 1. Eight cases involved students, and the ninth case involved a staff member.