Fig 1.
Model chain to simulate SARS-CoV-2 transmission in indoor spaces.
Fig 2.
Effect of contact intensity on exposure and the relative contribution to exposure of transmission routes.
A) exposure for 15 minutes at increasing distance, B) exposure at 1.5 metres for an increasing duration, C and D) as A and B but when the infectious individual was present 3 hours prior to the contact occurring, allowing for a buildup of virus in the environment. Red dashed lines show the contact with 1.5 metres and 15 mins. Exposure is shown relative to this benchmark, in a scenario of concurrent arrival of the infectious and susceptible individuals (as shown in A and B). For instance, a relative exposure of 25 means that overall exposure is 25 times that of the exposure of a benchmark contact. Individuals do not share common surfaces in this experiment, thus exposure from the fomites routes is negligible.
Fig 3.
Effect of different respiratory activities on exposure.
A) The relative emission rate of virions and B) the relative exposure during talking and singing continuously for 15 mins, relative to breathing. C) The relative contribution of the three transmission routes to the individual’s exposure while breathing, talking and singing. Both the infectious and susceptible individuals are assumed to perform the respective respiratory activity. Individuals do not share common surfaces in this experiment, thus exposure from the fomites routes is negligible.
Fig 4.
The impact of interventions on exposure after 15 minutes at a 1.5-metre distance.
A) The impact of ventilation air change rate per hour (ACH) on exposure. The red dashed line shows the baseline ACH = 3 per hour indoors. B) The impact of mask-wearing by both infectious and susceptible individuals on virus exposure. The default filter efficiency is assumed to be 40% for aerosols (red dashed line). The exposure load for contact at 1.5m and 15 min without a mask and with poor ventilation (ACH = 0) is standardised to 1.
Fig 5.
The trajectory, seat locations and the visiting duration of each individual in a simulation.
(A) the trajectory of the infectious individual (ID = 9). (B) the trajectories of other 31 individuals with individual 25 sits in the same seat as Individual 9. (C) the visiting time of all individuals with the orange shade shows the visiting time of the infectious individual.
Fig 6.
Cumulative virus contamination in the environment.
(A) aerosols, (B) droplets, and (C) on fomites. Contamination is expressed as the virion quantity relative to an average infectious individual’s hourly emission.
Fig 7.
Susceptible individuals’ exposure load.
Exposure load is expressed as the virion quantity relative to an average infectious individual’s hourly emission and is partitioned by transmission route. The exposure of susceptible individuals with the red dashed line showing the exposure for a benchmark contact of 1.5m for 15min.
Table 1.
Sensitivity analysis on the impact of route specific dose-response relationships on the number of infected individuals (default in bold).
Fig 8.
The impact of face masks and ventilation on virus exposure in the case study.
(A,B,C) a scenario where individuals do not wear face masks and an ACH is 0 (A), 3 (B), and 6 (C) per hour in the restaurant, (D, E) a scenario where people wear face masks when moving and an ACH of 3 (D) and 6 (E). The dashed red line indicates the expected exposure of a benchmark contact of 1.5m for 15 minutes.
Fig 9.
The density distributions of the expected number of infected individuals in the case study for varying route-specific transmission efficiency.
Each row shows a parameter setting for croute: (A) croute is the same for all routes (caerosols:cdroplets:cfomites is 10%:10%:10%). (B) croute is smaller for fomites (caerosols:cdroplets:cfomites is 10%:10%:1%). (C) croute is smaller for fomites and droplets (caerosols:cdroplets:cfomites is 10%:1%:1%). (D) croute is smaller for fomites and aerosols (caerosols:cdroplets:cfomites is 1%:10%:1%). Each column shows an intervention scenario: (a) poor ventilation scenario, ACH = 0, (b) baseline scenario, ACH = 3, (c) scenario with recommended ventilation, ACH = 6, (d) baseline scenario with face masks worn while moving, (e) scenario with recommended ventilation and with face masks worn while moving. The black solid lines indicate the mean value of the infected number in the baseline scenario and the dashed lines show the mean value corresponding to each respective intervention scenario. Fig 9Ab (in bold border) shows the baseline scenario.
Fig 10.
Illustrative NOMAD floor field with two resulting trajectories ([100]).
The white rectangle (on the top) represents the entrance, grey rectangles represent the tables which also act as obstacles, the transparent rectangles around the tables are chairs that represent the destinations, coloured areas in the middle show how the walking cost fields are shaped over the space, and the red and blue lines are examples of the preferred path a pedestrian would follow.
Table 2.
Parameters for activity scheduler and pedestrian model.
Fig 11.
Schematic of processes in the epidemiological model.
Table 3.
Parameters for the transmission model.