Silent Spreaders: Asymptomatic COVID-19 Transmission Dynamics in University Dormitories

Claire Bernard¹, Jing Chen², Matteo Romano³

Abstract

Background:
University dormitories are high-density environments where asymptomatic SARS-CoV-2 carriers can contribute to rapid viral spread, often undetected until symptomatic cases appear.

Objective:
To quantify the contribution of asymptomatic infections to total COVID-19 transmission in university dormitories.

Methods:
A prospective cohort study was conducted in three universities in France between October 2022 and March 2023. Weekly PCR testing was performed on 1,842 dormitory residents, regardless of symptoms. Contact tracing identified secondary attack rates. Viral load (Ct values) was compared between asymptomatic and symptomatic cases.

Results:
Of 426 confirmed cases, 38.7% were asymptomatic at detection. The secondary attack rate from asymptomatic index cases was 11.8%, compared to 17.4% for symptomatic cases (p = 0.04). Median viral loads were not significantly different (Ct 23.1 vs. 22.7, p = 0.42). Asymptomatic carriers accounted for 28% of all transmission events.

Conclusion:
Asymptomatic SARS-CoV-2 carriers play a substantial role in transmission in dense living environments. Routine periodic testing in dormitories could prevent large outbreaks.