Are colleges Covid-19 superspreaders? Cases went up by 56% in counties where classes were in person, says CDC

A Stanford University analysis shows in 17 of the campuses monitored, outbreaks translated directly into peaks of infection within their home counties


                            Are colleges Covid-19 superspreaders? Cases went up by 56% in counties where classes were in person, says CDC
College campuses might actually be superspreaders (Getty Images)

Reopening college campuses during the Covid-19 pandemic remains a topic of ongoing debate. According to researchers, college campuses are at risk of becoming Covid-19 superspreaders for the entire county. An analysis by the US Centers for Disease Control and Prevention (CDC) suggests that US counties, where large colleges and universities opened for in-person classes in the fall, saw a massive spike in the incidence of Covid-19.

Counties with large colleges or universities with remote instruction (22) experienced a 17.9% decrease in incidence. However, university counties with in-person instruction (79) saw a 56.2% increase (from 15.3 to 23.9 cases per 100,000) in incidence, comparing the 21-day periods before and after classes started. Counties without large colleges or universities (3,009) experienced a 5.9% decrease in incidence during a similar time frame.

The researchers advise that mitigation strategies may be especially important for colleges and universities in areas where transmission from students into the broader community could exacerbate existing disparities, including access to and utilization of healthcare. “In-person instruction at colleges and universities was associated with increased county-level Covid-19 incidence and percentage test positivity. Implementation of increased mitigation efforts at colleges and universities could minimize on-campus Covid-19 transmission,” recommend authors.

Remote-instruction university counties had a 17.9% decline in Covid-19 incidence
(Getty Images)

Some university counties might have one or more concerning factors, such as higher levels of older adult populations, high rates of obesity and cardiovascular disease, or strained healthcare resources. “These counties might need to consider the implications of in-person instruction on the spread of Covid-19 among a student population that might have interactions with persons at higher risk in the community. College and university administrators should work with local decision-makers and public health officials to strengthen community mitigation,” suggest experts.

The team, which also includes experts from the US Department of Health and Human Services (HHS), examined fall class schedules posted to large college and university websites in the US. They looked at which institutions held remote or in-person classes in early September 2020. The report also analyzed non-university counties. The percentage of counties identified at least once as a hotspot increased for all three groups, with the highest percentage observed in in-person instruction university counties (30.4% absolute increase), followed by remote-instruction university counties (9.1%) and non-university counties (1.5%).

Campus outbreaks can spread into neighboring communities

Many institutions that reopened cautiously in the fall experienced a massive wave of infections, and colleges were soon declared as the new hotspots of the pandemic. A separate study now shows the precise effects of college outbreaks on their immediate neighborhood. It cautions that the first two weeks of instruction present a high-risk period for campus outbreaks and that these outbreaks tend to spread into the neighboring communities.

The first two weeks of instruction present a high-risk period for campus outbreaks (Getty Images)

Looking at 30 campuses across the nation with the highest amount of reported cases, experts say that 14 had spikes — at their peak — which were well above 1,000 coronavirus cases per 100,000 people per week within the first two weeks of class. This is an order of magnitude larger than the nationwide peaks of 70 and 150 during the first and second waves of the pandemic, explains the team.

While most colleges were able to rapidly reduce the number of new infections, many failed to control the spread of the virus beyond their campus. In some colleges, one in five students had been infected with the virus by the end of the fall term. Four institutions had over 5,000 cases, reveal findings published in Computer Methods in Biomechanics and Biomedical Engineering.

Within only two weeks, in 17 of the campuses monitored, a new computer model developed by scientists at Stanford University shows that outbreaks translated directly into peaks of infection within their home counties. “Strikingly, these local campus outbreaks rapidly spread across the entire county and triggered a peak in new infections in neighboring communities. Our results confirm the widespread fear in early fall that colleges could become the new hot spots of Covid-19 transmission,” says senior author Ellen Kuhl.

Coronavirus cases across 30 college campuses in the US (A data-driven modeling study - Lu et al, Computer Methods in Biomechanics and Biomedical Engineering)

Lead author Hannah Lu, from Stanford’s Energy Resources Engineering program, explains that policymakers often use an incidence of 50 coronavirus cases per 100,000 people per week as a threshold for high-risk counties, states, or countries. “All 30 institutions in our study exceeded this value, three even by two orders of that magnitude. The number of students who had become infected just throughout the fall is more than twice of the national average since the beginning of the outbreak of 5.3%, with 17.3 million reported cases at a population of 328.2 million,” she states.

All reported campuses pursued regular surveillance testing, weekly or even twice per week, combined with aggressive test-trace-isolate strategies. Tight oversight proved critical, especially during the first two weeks of class, when almost half of the institutions experienced a massive spike in new cases, say investigators. 

Campuses pursued regular surveillance testing (Getty Images)

“Interestingly, the majority of colleges and universities were able to rapidly manage their outbreaks and suppress campus-wide infections, while the neighboring communities were less successful in controlling the spread of the virus. As a result, for most institutions, the outbreak dynamics remained manageable throughout the entire fall of 2020 with narrow spikes of less than 300 cases per day,” the findings state.

The research team believes that this methodology, in combination with continuing online learning, is the best way to prevent college sites from becoming the major hub of the disease. They say that tight outbreak management, for example, the immediate transition from in-person to all online learning, can reduce the peaks within about two weeks.

“Taken together, our study suggests that it is possible for colleges and universities to reopen safely while controlling the spread of Covid-19. We anticipate that tight test-trace-quarantine strategies, flexible transition to online instruction, and most importantly, compliance with local regulations will be critical to ensure a safe campus reopening after the winter break,” the experts conclude.

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