Is the daily use of public transport facilities an enhanced epidemiological risk for diagnosing COVID-19 among healthcare workers with mild respiratory symptoms?

Abstract

Introduction: Many people in Switzerland think that the daily use of the public transport facilities, during a pandemic peak wave, could be associated with an enhanced risk for Covid-19. Objectives: To investigate the association between the daily use of the public transport and acquisition of Covid-19 in Zurch during a peak wave of the pandemics. Methods: Retrospective cohort analysis of hospital-own databases at the Balgrist University Hospital in Zurich, between 1 October and 31 December 2020. We specifically interviewed our healthcare workers (HCW) about the use of public transport (with mandatory masking). Results: During the three most intensive months of the 2nd wave, we investigated 376 episodes of Covid-19-compatible respiratory symptoms and exposures among our HCW (median age 37 years), of which 94 (25%) revealed a positive PCR result for Covid-19. Overall, 225 HCW (225/376;60%) reportedly used the public transport (train, bus, tramway). In group comparison, the HCWs using the public transport system acquired no more Covid-19 than using a private transport (58/225 vs. 36/151;Pearson-chi2-test;p = 0.67). We added a logistic regression model with the outcome “Covid-19 infection” to adjust for the case-mix of different localizations or opportunities of potential contamination such as a documented exposure in the hospital, among the team members, in the family, or after a close contact to a PCR-confirmed case. In the multivariate results, using the public transport was irrelevant concerning the acquisition of Covid- 19 (odds ratio (OR) 0.98, 95%CI 0.59-1.62), in contrast, for example, to being exposed to a sick team member (OR 2.28, 95%CI 1.20-4.34). Conclusion: In Zurich, the daily use of public transport was not associated with an additional risk of being diagnosed with Covid-19 among the young population of HCWs, not even during the peak of a pandemic wave. Other factors are more relevant