Across the United States, the return of students to college campuses during the Covid-19 pandemic in fall 2020 sparked widespread fears that local communities would be overwhelmed by the virus.

But a new study from Washington State University challenges this narrative, demonstrating that in Pullman, returning students that year were not the primary drivers of community transmission, suggesting the effectiveness of mitigation strategies and the distinct nature of student and community spread.

While some university towns experienced surges in caseloads linked to returning students, the WSU study found that was not the case universally. Published in the journal Epidemiology, the study found “outbreaks” during the fall 2020 semester among students and in the community were largely independent and driven by cases originating from outside the area rather than local transmission. Very likely, mitigation efforts – like testing, social distancing and masks – were effective in limiting the spread of the virus.

“Going forward, it’s crucial to carefully evaluate the type and extent of transmission before deciding to shut down educational programs,” said Erin Clancey, a research professor and quantitative biologist in WSU’s Paul G. Allen School for Global Health who served as co-lead author for the study, in a news release. “We found that mitigation efforts were effective and can allow schools and universities to keep operating safely.”

Clancey, whose research uses mathematical and statistical models to study complex biological processes, collaborated with her peer in the Allen School, Eric Lofgren, an infectious disease epidemiologist, and his former graduate student, Matthew Mietchen, now a postdoctoral research associate at the University of North Carolina.

During fall 2020, all WSU courses were fully remote, and campus housing was closed except for special exemptions. Many students, though, returned to Pullman, living off campus in apartments or Greek housing. Within the first three weeks of the semester, Whitman County reported one of the highest Covid-19 rates in the nation.  

Using advanced mathematical models, Clancey and colleagues analyzed case data from Whitman County to estimate transmission rates within and between the student and community subpopulations and the extent of cross-transmission.

They found student Covid-19 cases peaked in the first two weeks of the semester before declining and then briefly spiking ahead of Thanksgiving. This suggests the initial rise was the result of already infected students arriving in Pullman and not widespread student-to-student transmission. The short-lived increase before Thanksgiving may have been driven by expanded testing before students returned home for the holiday.

Community cases didn’t begin rising until late October and early November. This staggered timing indicates limited virus transmission between the two populations.

“The data show that the outbreaks among students and the community were largely separate and happened at different times,” Clancey said. “What we found is there was transmission in each population, but across them, it was very, very minimal.”

Clancey said there are several contributing factors, including that students are largely concentrated in housing on or near the WSU campus separate from the community at large. Social distancing, mask mandates and restrictions on bars and large gatherings also reduced opportunities for virus spread between students and community members.

“Students tended to naturally isolate from the rest of Pullman,” Clancey said. “The lack of social mixing between students and the community was an important factor in limiting cross-transmission. I think natural behavior is keeping these populations separate – which is characteristic of many college towns.”

Clancey suggests additional testing of students as they returned to campus could have further limited the initial outbreak.

Rather than defaulting to shutting down schools, she added, measures can be tailored to the specific patterns of transmission in each setting.

“Understanding how different groups interact during an epidemic helps us design smarter, less disruptive mitigation strategies,” Clancey said. “This knowledge can guide future responses to respiratory diseases and help protect both educational institutions and the communities that host them.”