Passively sensing SARS-CoV-2 RNA in public transit buses

Abstract

Affordably tracking the transmission of respiratory infectious diseases in urban transport infrastructures can inform individuals about potential exposure to diseases and guide public policymakers to prepare timely responses based on geographical transmission in different areas in the city. Towards that end, we designed and tested a method to detect SARS-CoV-2 RNA in the air filters of public buses, revealing that air filters could be used as passive fabric sensors for the detection of viral presence. We placed and retrieved filters in the existing HVAC systems of public buses to test for the presence of trapped SARS-CoV-2 RNA using phenol-chloroform extraction and RT-qPCR. SARS-CoV-2 RNA was detected in 14% (5/37) of public bus filters tested in Seattle, Washington, from August 2020 to March 2021. These results indicate that this sensing system is feasible and that, if scaled, this method could provide a unique lens into the geographically relevant transmission of SARS-CoV-2 through public transit rider vectors, pooling samples of riders over time in a passive manner without installing any additional systems on transit vehicles.

Negligible risk of surface transmission of SARS-CoV-2 in public transportation

“…Studies comparing surface and air samples collected in the same environment usually report significant differences in SARS-CoV-2 RNA prevalence between air and surface samples. Nevertheless, some authors report higher prevalence in surface swabs, 15 , 37 , 38 others in air samples 39 and others similar prevalence rates for both. 40 , 41 The reasons for this as well as for the overall variability could be (amongst others) related to differences in sampling and detection methods and the tools used, as well as to the intensity of public transport use, the actual COVID-19 incidence, properties of the currently circulating strains, environmental conditions and cleaning and disinfection procedures.…”

A 17-month longitudinal environmental sampling study carried out on public transport vehicles operating in England during the COVID-19 pandemic identified low levels of SARS-CoV-2 RNA contamination

“…Studies with volunteers have shown that SARS-CoV-2 RNA can be shed in aerosol particles in exhaled breath by people with a SARS-CoV-2 infection during respiratory activities such as breathing and talking, particularly during early stages of infection (Adenaiye et al, 2022; Ma et al, 2021; Tan et al, 2023). Previous studies in public transport have detected SARS-CoV-2 RNA in air samples taken on buses and from associated air conditioning filters (Hadei et al, 2021; Hoffman et al, 2022; Moreno et al, 2021). Others have not (Di Carlo et al, 2020), probably reflecting differences in sampling methodologies, prevalence of COVID-19 in the community, mitigation strategies (e.g.…”

“…Data collection can inform policy decisions and refine modelling assumptions. Several studies have investigated the presence of SARS-CoV-2 RNA in public transport vehicles (Caggiano et al, 2021; Di Carlo et al, 2020; Hadei et al, 2021; Hoffman et al, 2022; Moreno et al, 2021). However, these studies have been carried out over short sampling timeframes.…”

Detection of SARS-CoV-2 in drainage systems from tourist buses and bus station in Mexico

“…La presencia de SARS-CoV-2 en el transporte público ha sido ampliamente estudiada a nivel mundial, centrándose en la detección de diferentes tipos de matrices. Hoffman et al (2022) detectaron 5/37 muestras positivas de filtros de aire en autobuses públicos en Seattle, Washington, EE. UU.…”

“…De acuerdo con las diferentes opiniones y percepciones sobre la seguridad o el riesgo de transmisión del SARS-CoV-2 en espacios cerrados como el transporte público, se han realizado varios estudios enfocados en la detección de ARN viral en diversas matrices ambientales como https://doi.org/10.15741/revbio.11.e1631 ISSN 2007-3380 aerosoles, sistemas de filtración de aire, superficies como pasamanos, botones y manijas de asientos en autobuses, estaciones de trenes y autobuses, detectando la presencia del virus en todas las muestras mencionadas (Caggiano et al, 2021;Singh et al, 2021;Hoffman et al, 2022;Gomes da Silva 2022). El desarrollo de este tipo de estudios contribuye a comprender y estimar el riesgo potencial de la presencia de pasajeros conscientes o inconscientes de ser positivos para COVID-19, factor de transmisión del SARS-CoV-2 en el transporte público; por esa razón, el propósito de este estudio fue detectar la presencia de ARN del SARS-CoV-2 en agua residual de tanques contenedores de sanitarios de autobuses nacionales e internacionales.…”