Kristen K Bjorkman1, Tassa K Saldi1, Erika Lasda1, Leisha Conners Bauer2, Jennifer Kovarik2, Patrick K Gonzales1, Morgan R Fink1, Kimngan L Tat1, Cole R Hager1, Jack C Davis1,3, Christopher D Ozeroff1,3, Gloria R Brisson4, Daniel B Larremore1,5, Leslie A Leinwand1,3, Matthew B McQueen6,7, Roy Parker1,8,9. 1. BioFrontiers Institute, University of Colorado Boulder, Boulder, Colorado, USA. 2. Health Promotion, University of Colorado Boulder, Boulder, Colorado, USA. 3. Department of Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, USA. 4. Medical Services, University of Colorado Boulder, Boulder, Colorado, USA. 5. Department of Computer Science, University of Colorado Boulder, Boulder, Colorado, USA. 6. Department of Integrative Physiology, University of Colorado Boulder, Boulder, Colorado, USA. 7. Institute for Behavioral Genetics, University of Colorado Boulder, Boulder, Colorado, USA. 8. Howard Hughes Medical Institute, University of Colorado Boulder, Boulder, Colorado, USA. 9. Department of Biochemistry, University of Colorado Boulder, Boulder, Colorado, USA.
Abstract
BACKGROUND: The coronavirus disease 2019 pandemic spread to >200 countries in <6 months. To understand coronavirus spread, determining transmission rate and defining factors that increase transmission risk are essential. Most cases are asymptomatic, but people with asymptomatic infection have viral loads indistinguishable from those in symptomatic people, and they do transmit severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, asymptomatic cases are often undetected. METHODS: Given high residence hall student density, the University of Colorado Boulder established a mandatory weekly screening test program. We analyzed longitudinal data from 6408 students and identified 116 likely transmission events in which a second roommate tested positive within 14 days of the index roommate. RESULTS: Although the infection rate was lower in single-occupancy rooms (10%) than in multiple-occupancy rooms (19%), interroommate transmission occurred only about 20% of the time. Cases were usually asymptomatic at the time of detection. Notably, individuals who likely transmitted had an average viral load approximately 6.5-fold higher than individuals who did not (mean quantification cycle [Cq], 26.2 vs 28.9). Although students with diagnosed SARS-CoV-2 infection moved to isolation rooms, there was no difference in time to isolation between cases with or without interroommate transmission. CONCLUSIONS: This analysis argues that interroommate transmission occurs infrequently in residence halls and provides strong correlative evidence that viral load is proportional to transmission probability.
BACKGROUND: The coronavirus disease 2019 pandemic spread to >200 countries in <6 months. To understand coronavirus spread, determining transmission rate and defining factors that increase transmission risk are essential. Most cases are asymptomatic, but people with asymptomatic infection have viral loads indistinguishable from those in symptomatic people, and they do transmit severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, asymptomatic cases are often undetected. METHODS: Given high residence hall student density, the University of Colorado Boulder established a mandatory weekly screening test program. We analyzed longitudinal data from 6408 students and identified 116 likely transmission events in which a second roommate tested positive within 14 days of the index roommate. RESULTS: Although the infection rate was lower in single-occupancy rooms (10%) than in multiple-occupancy rooms (19%), interroommate transmission occurred only about 20% of the time. Cases were usually asymptomatic at the time of detection. Notably, individuals who likely transmitted had an average viral load approximately 6.5-fold higher than individuals who did not (mean quantification cycle [Cq], 26.2 vs 28.9). Although students with diagnosed SARS-CoV-2 infection moved to isolation rooms, there was no difference in time to isolation between cases with or without interroommate transmission. CONCLUSIONS: This analysis argues that interroommate transmission occurs infrequently in residence halls and provides strong correlative evidence that viral load is proportional to transmission probability.
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