Natural ventilation as a means of airborne tuberculosis infection control in minibus taxis

Abstract

Airborne infection control measures are used extensively in health-care settings to curtail the spread of airborne infectious diseases. Few such measures are applied in public congregate spaces outside health facilities, such as those associated with public transport. In minibus taxis – a popular form of public transport in South Africa – poor ventilation creates conditions that allow for transmission of airborne diseases, particularly tuberculosis. In this study, we focused on developing quantitative ventilation profiles for the 16-seater Toyota Quantum Ses’fikile model commonly used in the Cape Town metropole. We studied the ventilation rates achievable in an occupied taxi under varying operational conditions, such as driving speed and open window configurations, which were based on observations made during preliminary taxi journeys. Two open-window configurations were found to provide ventilation rates close to or exceeding WHO recommended per-person requirements for high-risk clinical areas and are therefore likely to be effective in reducing the risk of tuberculosis transmission.

COVID-19 transmission and control in land public transport: A literature review

“…According to Li et al [83] , when opening the front windows of a school bus, the ventilation was better than opening the middle windows. The same applied to the minibus and taxis, only opening the front windows provided the most ventilation compared to only opening the middle windows or the rear windows [84] . Moreover, inlet ports at the frontal and sunroof could also effectively carry fresh air into the vehicle [48 , 54 , 81 , 85] .…”

“…The size of ventilation openings is also a factor that affects natural ventilation. Several studies found a notable improvement in the ventilation rate when opening windows increased to two pairs from one pair [48 , 83 , 84] . Two pairs of opening windows could supply ventilation rates close to even exceeding WHO recommended per-person requirements for high-risk clinical areas [84] .…”

“…Several studies found a notable improvement in the ventilation rate when opening windows increased to two pairs from one pair [48 , 83 , 84] . Two pairs of opening windows could supply ventilation rates close to even exceeding WHO recommended per-person requirements for high-risk clinical areas [84] . Therefore, it is very important for proper circulation and renewal of air to leave at least two open windows.…”

A Sanitation Argument for Clean Indoor Air: Meeting a Requisite for Safe Public Spaces

“…Models of infectious disease transmission show that improved ventilation can mitigate outbreaks of influenza ( 66 ), seasonal variations in ventilation (less ventilation during winter) can increase risks of airborne disease transmission in classrooms ( 67 ), improved air quality reduces transmission risks of several airborne pathogens in clinics ( 68 ), and can also reduce disease transmission risks at a city level ( 69 ). A disease that is airborne and has epidemic proportions around the world, is tuberculosis and there are several studies linking improvement in ventilation with reduction in risks of tuberculosis infection ( 70 , 71 ).…”

Confirmation of HLA-II associations with TB susceptibility in admixed African samples

“…Several factors increase the risk of progressing to active TB, including co-infection with human immunodeficiency virus (HIV) and comorbidities, such as diabetes mellitus, asthma and other airway and lung diseases (Glaziou et al, 2018). Socio-economic factors including smoking, malnutrition, alcohol abuse, intravenous drug use, prolonged residence in a high burdened community, overcrowding, informal housing and poor sanitation also influence M.tb transmission and infection (Cudahy et al, 2020; Escombe et al, 2019; Laghari et al, 2019; Matose et al, 2019). Additionally, individual variability in infection and disease progression has been attributed to variation in the host genome (Uren et al, 2021; Verhein et al, 2018).…”