Fig 1.
Patients typically enter the clinic through the entrance on the bottom left, register at the reception, then wait in the waiting room or along the corridor until they see a doctor in one of the care rooms or the TB room. They exit the clinic through one of the exits in the waiting room or at the end of the corridor. Colored icons show the placement of the video sensors to track person movements and the devices monitoring CO2 levels.
Fig 2.
Examples of person movements in the clinic.
Fig 3.
Visual summary of the spatiotemporal modeling approach.
(1) Clinical records and person movements were linked based on their timestamps at the registration to determine the spatiotemporal location of diagnosed (infectious) TB patients. (2) Both diagnosed and randomly selected undiagnosed TB patients among clinic attendees generate infectious quanta. (3) Person-tracking and environmental data were combined to estimate the air change rate. (4) Air change rate was related to the speed at which quanta diffuses indoors. (5) The air change rate also determines quanta removal through outdoor air exchange, in addition to inactivation of Mtb in airborne particlesparticles… and removal through gravitational settling. (6) Quanta generation, diffusion, and removal determine the spatiotemporal quanta concentration, from which the personal risk of infection is calculated using the Wells-Riley equation.
Fig 4.
Person tracks and environmental conditions by clinic area.
Across clinic days and for the clinic waiting room, corridor and TB room: (a) total number of tracks recorded per unit space, (b) number of people in the clinic over time, (c) time per clinic visit, and (d) air change rates. Lines and ribbons show the mean plus/minus standard deviation. Boxplots show the medians as lines, interquartile ranges as boxes, ranges as whiskers, and outliers as dots.
Fig 5.
Spatiotemporal quanta concentration by clinic area.
Model-estimated average quanta concentrations during clinic days in the morning and afternoon in the clinic’s waiting room, corridor and TB room of the clinic.
Fig 6.
Impact of infection control measures.
Mean risk of infection per clinic attendee (median visit time 25 min, IQR 13 min–46 min): (a) with mask use (community or surgical masks) and high ventilation as observed during the COVID-19 pandemic, (b) without mask use and high ventilation, (c) with mask use and normal ventilation as observed before the COVID-19 pandemic (d) without mask use and normal ventilation. Low risk: < 0.1%, Medium: 0.1–1%, High: > 1% risk of infection.