Urban rail transport and SARS-CoV-2 infections: an ecological study in Lisbon Metropolitan Area

ABSTRACT Introduction Large number of passengers, limited space and shared surfaces can transform public transportation into a hub of epidemic spread. This study was conducted to investigate whether proximity to railway stations, a proxy for utilization, was associated with higher rates of SARS-CoV-2 infection across small-areas of Lisbon Metropolitan Area (Portugal). Methods The number of SARS-CoV-2 confirmed infections from March 2 until July 5, 2020 at parish-level was obtained from the National Epidemiological Surveillance System. We used a Geographic Information System to estimate proximity to railway stations from the six railway lines operating in the area. Then, we fitted a quasi-Poisson generalized linear regression model to estimate the relative risks (RR) and corresponding 95% Confidence Intervals (95%CI). Results Between May 2 and July 5, 2020, there were a total of 17,168 SARS-CoV-2 infections in the Lisbon Metropolitan Area, with wide disparities between parishes. Globally, parishes near one of the railway lines (Sintra) presented significantly higher SARS-CoV-2 infection rates (RR=1.42, 95%CI 1.16, 1.75) compared to those parishes located far away from railway stations, while the opposite happened for parishes near other railway lines (Sado/Fertagus), whose infection rates were significantly lower than those observed in parishes located far away from railway stations (RR=0.66, 95%CI 0.50, 0.87). However, the associations varied according to the stage of the epidemic and according to mitigation measures in place. Regression results also revealed an increasing influence of socioeconomic deprivation on SARS-CoV-2 infections. Conclusions We found no consistent association between proximity to railway stations and SARS-CoV-2 infection rates in the most affected metropolitan area of the country, suggesting that other factors (e.g. socioeconomic deprivation) might play a more prominent role in the epidemic dynamics.