Impact of Ventilation on Respiratory Virus Transmission in College Residence Hall Cohorts: Potential for Causal Inference About Mode of Transmission.

BACKGROUND

The SARS-CoV-2 pandemic focused attention on airborne-inhalation transmission and building ventilation. However, investment in solutions lags because few epidemiologic studies demonstrate a causal effect of ventilation on acute respiratory infection (ARI) transmission. This highlights a need for improved study designs to support causal inference.

METHODS

To investigate the potential for causal inference, we analyzed prospective cohorts residing in a high-ventilation (HVent, ≥ 5 L/s per person) or a neighboring low-ventilation (LVent, < 5 L/s per person) college residence hall during two spring semesters (2018 and 2019). Swab samples, analyzed using a PCR panel for respiratory pathogens, were collected based on self-reported symptoms and contacts. Our analysis focused on roommate pairs where both had been tested within a 2-week period. Roommate pairs with concordant positive PCR results were categorized as possible transmission events. We used genetic sequencing and phylogenetic analysis to identify probable transmission clusters and events.

RESULTS

We analyzed data from 368 cohort participants (82 HVent and 286 LVent), including 60 person-infections, with a trend toward 54% lower ARI risk among students living in HVent versus LVent residence halls. We identified 97 roommate pairs, 64 two-week intervals where both members were tested, 36 (2 HVent and 34 LVent) intervals with ≥ 1 infection, and four possible transmission events (all LVent). Sequence data available for two of the four events confirmed one probable transmission cluster and one probable transmission event.

CONCLUSIONS

Future college dorm transmission studies should prioritize enrolling roommates rather than individuals, measuring ventilation, and confirming transmission events through whole genome sequencing.