Modeling the factors that influence exposure to SARS‐CoV‐2 on a subway train carriage

Abstract

We propose the Transmission of Virus in Carriages (TVC) model, a computational model which simulates the potential exposure to SARS‐CoV‐2 for passengers traveling in a subway rail system train. This model considers exposure through three different routes: fomites via contact with contaminated surfaces; close‐range exposure, which accounts for aerosol and droplet transmission within 2 m of the infectious source; and airborne exposure via small aerosols which does not rely on being within 2 m distance from the infectious source. Simulations are based on typical subway parameters and the aim of the study is to consider the relative effect of environmental and behavioral factors including prevalence of the virus in the population, number of people traveling, ventilation rate, and mask wearing as well as the effect of model assumptions such as emission rates. Results simulate generally low exposures in most of the scenarios considered, especially under low virus prevalence. Social distancing through reduced loading and high mask‐wearing adherence is predicted to have a noticeable effect on reducing exposure through all routes. The highest predicted doses happen through close‐range exposure, while the fomite route cannot be neglected; exposure through both routes relies on infrequent events involving relatively few individuals. Simulated exposure through the airborne route is more homogeneous across passengers, but is generally lower due to the typically short duration of the trips, mask wearing, and the high ventilation rate within the carriage. The infection risk resulting from exposure is challenging to estimate as it will be influenced by factors such as virus variant and vaccination rates.

Modeling the effect of temperature and relative humidity on exposure to SARS‐CoV ‐2 in a mechanically ventilated room

“…The decay in the viability of the virus in droplets was not included. While some of these effects could be included in a CFD model, it would be more effective to include others in a higher‐level model, such as a quantitative microbiological risk assessment model 41 …”

Impact of pre-pandemic travel mobility patterns on the spatial diffusion of COVID-19 in South Korea

“…In addition, the link between COVID-19 transmission and public transportation has been found to be mixed ( Gartland et al, 2022 ). While using public transportation, measures such as the wearing of masks, physical distancing, air conditioning, and filtering on public transit may contain the spread of COVID-19 effectively (Kriegel, 2022; Miller et al, 2022 ; Muathesis, 2022; Yang et al, 2022 ). Quarantine measures, such as suspension of operations or restrictions to prevent the spread of infectious diseases, may cause unexpectedly high socioeconomic costs, such as increases in mental health conditions and the deepening of socioeconomic inequality ( Fink et al, 2022 ; Koch and Park, 2022 ; Thunström et al, 2020 ).…”

“…They also argued that the routes and main factors of public transit in diffusing COVID-19 were still unclear during the early experiences of the pandemic. Some studies have found that such measures such as mask wearing, physical distancing, air conditioning, and filtering on public transit have a significant impact on reducing exposure to COVID-19 transmission ( Kriegel et al, 2021 ; Matheis et al, 2022 ; Miller et al, 2022 ; Yang et al, 2022 ). Musselwhite et al (2020) argues that restrictions on the operation of overcrowded public transit due to the higher possibility of individual transmission of COVID-19 needs to be well thought because the exposure in households can be higher.…”

Laboratory Evaluation of a Quaternary Ammonium Compound-Based Antimicrobial Coating Used in Public Transport during the COVID-19 Pandemic

“…However, the role that public transport plays in the transmission of infectious diseases is not well-understood, although there is some epidemiological evidence that it could contribute to the transmission of influenza-like illness ( 7 , 8 ), and high-touch surfaces on public transport vehicles are known to be contaminated with bacteria ( 9 ) and can be contaminated with SARS-CoV-2 RNA ( 10 , 11 ). A recent modeling study that compared the relative contributions of close-range exposure to SARS-CoV-2 (via droplets or aerosols), airborne exposure (via small aerosols without having to be within 2 meters of the infectious source), and exposure via contaminated fomites in a subway carriage concluded that all three routes of transmission are relevant in this setting ( 12 ).…”