DISPERS

The Covid-19 pandemic highlighted the link between infectious disease transmission and the built environment. Occupancy density and time spent in enclosed spaces contribute to increase the spread of pathogens within populations. Therefore, they were structuring elements in the measures taken for the management of the pandemic, with closures or implementation of gauges in our daily life places (work, schools, leisure, restaurants...). This crisis has also revealed the effectiveness of physical distancing and hand hygiene measures to counteract contamination routes by direct or indirect contact. On the other hand, the modalities of exposure to an emission of aerosols containing pathogens, in particular from the respiratory tract, and the management of these infectious aerosols have not yet found satisfactory answers. In France and internationally, many teams have worked to model the transport and exposure of occupants of indoor environments to SARS-Cov-2 aerosols. However, whatever the level of precision and the approach adopted, those studies still lack experimental data to strengthen their projection and propose a robust assessment of the risk of airborne transmission. One of the first objectives of the project will be to characterize the "source term" for which data are still lacking, namely: i) the emission rate, ii) the viral load contained during the first phase of excretion, and iii) the initial size and biochemical composition of the microdroplets carrying infectious viruses. On the other hand, recent epidemics have also brought to the forefront the need to better understand the mechanisms of virus transmission in relation to their persistence in the air. Studies in this field are mainly observational studies carried out in laboratories, in predefined experimental contexts and relatively distant from the reality of the exposure modalities. The modelling of the persistence mechanisms of airborne pathogens, and especially of the capacity of viruses to remain infectious in respiratory droplets in proximity or far from the emission source will allow the emergence of innovative solutions of biosecurity for the built environments. Based on data collected, biological and biochemical mechanisms that can explain the inactivation of viruses in the air will be proposed, in a more global approach. The formulation of these mechanisms will also rely on studies carried out in other fields apart from virology. Consequently, the DISPERS project aims at building an explanatory aerosol persistence model, based on robust and exploitable experimental data obtained in realistic exposure situations. The experimental strategy, supported by a transdisciplinary approach, aims to develop the experimental means necessary for the characterization of the source term (animal or human) and to study the survival dynamics of biological aerosols in the laboratory. A key point of this approach will be to work in a controlled way on the whole chain of contamination on an animal model, from the characterization of the emissions of the pig contaminated by a type A influenza virus, to the study of its infectivity according to controlled abiotic conditions which will have been previously explored in laboratory. Then, this initial model will be extended to other models of interest in human and animal health, and NRBC.