Predicting infection routes: GRS team calculates the spread of SARS-CoV-2 aerosols in indoor environments


© flickr/Rainer

In the current Covid 19 pandemic, airborne aerosols that contain viruses are considered to be an important transmission route, especially in insufficiently ventilated rooms. To be able to make a sound assessment of the related risk of infection and to derive appropriate recommendations for action, the aerosol behaviour as well as representative ambient conditions must be considered in detail and realistically. Within the framework of the AeroCoV research project, scientists of GRS have applied the COCOSYS simulation code – which was developed and validated for the analysis of accidents and severe accidents in containments of nuclear power plants – for the first time for calculating the dispersion of SARS-CoV-2 aerosols. The related research report has now been published.

3D visualisation of the patient's roomIn order to obtain reliable and meaningful results, the researchers simulated two real scenarios within the software: After having entered the main characteristics of SARS-CoV-2 as well as human respiratory activities and aerosol release processes into COCOSYS, they calculated a case study from research literature in a first step: The comparison of the results shows that the time course of the infection risk in an Italian pharmacy can be reproduced well under different conditions (before and after the lockdown). 

In a next step, the potential infection risk was calculated in a comprehensive use case in a room of a hospital and care facility. For this purpose, the room was virtually modelled in COCOSYS. The research team assumed that an infected person lives in the room and that work processes take place that are typical for a care facility.

Using COCOSYS to determine the risk of infection

In particular, the scientists were able to investigate the interaction of several factors – such as respiratory activity, concentration of virus-containing aerosols in the room air, room-related boundary conditions, varying temperature and humidity in the room, influence of air exchange and filter systems (masks) – in detail and over an adequate period of time. This clearly distinguishes the COCOSYS approach from simplified analytical approaches and computational fluid dynamics (CFD) calculations, on the basis of which it is hardly possible to derive scientifically justified recommendations for action in the context of aerosol dispersion within complex room geometries. Building on the AeroCoV project, subsequent work can be carried out to investigate scenarios with several rooms and more complex interactions between people (including various activities).

For the investigation of aerosol dispersion in indoor air, there are no restrictions with regard to the type of virus considered. The approach chosen here thus offers the possibility of transferring the knowledge gained to forthcoming dispersion pathways of infectious aerosols or mutations of the SARS Cov-2 virus and optimising actions and hygiene measures for the future.

Based on the results of the research report, a GRS developer team has also developed a new app: With “Aerosol Control”, users can determine their risk of infection with SARS-CoV-2 in a room. By entering various influencing factors (number of people in the room, length of stay, ventilation, etc.), the risk of infection can be calculated for different scenarios: a two-hour flight with 40 people, a 30-minute train journey with 10 mask-wearing fellow passengers in the compartment, or a three-hour meeting with a friend. The app will soon be available free of charge for iOS and Android.