By Rachel L. Graham, Ph.D.

CHAPEL HILL – The return to campus this fall for undergraduates of the UNC System was not without questions – from students, faculty, staff, support personnel, and the communities surrounding the campuses.

At UNC Chapel Hill, along with the other campuses in the UNC System, following the reduction of campus operations on March 20, outside of the medical campuses, operations transitioned to predominantly teleworking, with the exception of a small group of Communicable Disease Mandatory Employees who were permitted to report for on-campus duties.¹ Those individuals became accustomed to the regulations imposed in buildings and on buses and the health-monitoring expectations to prevent the spread of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), the virus that causes COVID-19.

When the UNC System announced its intention to start the semester with a modified program of in-person classes, the decision was met with concern from multiple directions. Students who would be returning to campuses were asked to sign a commitment to wear a mask, physically distance, and wash and sanitize their hands regularly. Students were warned of possibly being banned from campus or unenrolled from courses if they did not comply with these “Community Standards.”² It was an experiment that required strict compliance to be successful.

What it did not require was proof of a negative COVID test result prior to students returning.

At UNC-Chapel Hill, within a week of the start of the fall semester, the campus alert system had sent notifications of multiple COVID clusters in residence halls and fraternity and sorority houses. The University’s COVID-positive rate rose from 2.8% to 13.6%. Following these events, on August 17, the University announced that courses would transition to online only by August 19 and that campus would be de-densified in an effort to curb the spread of potentially fatal infection.³ 

Would proof of a negative COVID test result prior to any student’s return to campus have been an effective stopgap?

The immediate argument in favor of securing a negative COVID test prior to any change in location, particularly for movement that will result in a much more dense population at the destination, makes sense in concept. In a scenario where movements and behaviors can be carefully controlled, increasing the population density of susceptible, non-immune individuals would be safest if that population is stocked with individuals who have been given a certified clean bill of health. Viruses can’t reproduce outside their host cell. And by that definition, they must be ferried into a naïve population via a host – in this case, an infected human.

The factors that argue heavily against this approach in a real-life situation have their roots in the nature of the COVID tests themselves, and the nature of the virus they are designed to detect. COVID tests that are considered diagnostic come in two basic varieties: molecular and antigen. Molecular tests rely on the detection of a portion of the virus’ RNA genome. Antigen tests, conversely, rely on the detection of a portion of one of the viral proteins. Molecular tests are more sensitive than antigen tests, but results take more time (sometimes the same day, but usually more than one day), while antigen testing is considered a rapid test (results can be returned within 15 minutes).⁴ 

Both tests, however, rely on the virus to “set up shop” and replicate to high enough levels to meet the sensitivity thresholds. Neither test is capable of detecting infection at the point of exposure, or even one day after exposure. With the more-sensitive molecular test, a study found the probability of a false-negative result went from 100% on day 1 post-exposure to 67% on day 4 (still a very high rate), only dropping below 20% three days after symptom onset in some individuals.⁵

These delays between point of exposure and time of detection are bad enough when considering the desires of young adults to socialize with their friends after four months of quarantine. However, another, non-virus-related factor must be considered: testing delay. At many testing centers in Chapel Hill and across North Carolina in late July-early August, the delay between testing and receipt of results was seven days or more – an interval that is more than enough time for a false-negative result to transition to a positive result if the individual were re-tested. Faster test results were available, but usually at private testing centers, and for a fee, which would create equity issues for a public university.

These considerations, when factored into the knowledge that COVID-19 symptoms are mild – and, in some cases, nonexistent – in younger individuals make the logistics of assuring infection control among university populations with test results that may be over a week old daunting.

UNC-Chapel Hill, along with the UNC System, chose to act to preserve public health in the face of testing circumstances that are not ideal. These actions may seem to be erring on the side of conservative to some.

However, we are still in the first wave of the pandemic, and SARS-CoV-2 has not yet demonstrated signs of hypermutation in the face of selective pressure that the scientific community might have expected to see – a consideration that may come to the fore when therapeutics and vaccines become available in coming months.

We are unwitting witnesses to a historic event – the dissemination of a virus through a completely susceptible population. In this context, conservative actions and behaviors and each individual’s awareness of their impact on others are the best ways to preserve lives in the long run.

Rachel Graham is an assistant professor in the Department of Epidemiology in the Gillings School of Global Public Health at The University of North Carolina at Chapel Hill. She received her PhD in microbiology and immunology from Vanderbilt University in 2006, from the laboratory of Mark Denison, MD, after which she came to the UNC-Chapel Hill laboratory of Ralph Baric, PhD, to continue her studies.

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¹ https://www.unc.edu/posts/2020/03/17/reduced-operations/. 
² https://www.newsobserver.com/article244583977.html. 
³ https://www.dailytarheel.com/article/2020/08/breaking-remote.
⁴ https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html#anchor_1597521649237.⁵https://www.acpjournals.org/doi/10.7326/M20-1495.