Human Research Study of Particulate Propagation Distance from Human Respiratory Function

[Development of specific guidance for the safe opening and operation of recreational destinations under pandemic conditions]

Background

The SARS-CoV‑2 pandemic led to the closure of leisure and recreation facilities worldwide. As part of a model study funded by the Baden-Wuerttemberg Ministry of Social Affairs, Health and Integration, it was possible to demonstrate how a hygiene and safety concept can be successfully implemented in practice using the example of the opening and operation of an amusement park in Baden-Wuerttemberg (Germany) under scientific supervision.

Objective

The aim of the model project was, besides the verification of a possible infection event through a visit to the amusement park, to develop and review a recommended course of action for the safe opening and operation of leisure facilities under pandemic conditions, which can be transferred to other destinations.

Methods

A variety of data sources were used for this project: Recurrent expert rounds of multidisciplinary teams (business administration, healthcare research, sociology and medicine), aerosol measurement data, observation protocols, official infection statistics and interview data from visitor surveys.

Results

The action plan developed in this project provides guidance and recommendations for operators of recreation and leisure facilities to implement measures that enhance staff and guest safety, allowing facilities to operate under pandemic conditions.

Conclusion

This study sets a precedent using the example of a recreational park in Baden-Wuerttemberg (Germany) to serve as a guide for other facilities; however, operations in the leisure and tourism sector are unique and measures are accordingly difficult to transfer directly. The recommended action plan is further intended to support policy makers in future pandemic situations regarding measures to close, open and operate such facilities.

A Novel Framework for Modeling Person-to-Person Transmission of Respiratory Diseases

From the beginning of the COVID-19 pandemic, researchers assessed the impact of the disease in terms of loss of life, medical load, economic damage, and other key metrics of resiliency and consequence mitigation; these studies sought to parametrize the critical components of a disease transmission model and the resulting analyses were informative but often lacked critical parameters or a discussion of parameter sensitivities. Using SARS-CoV-2 as a case study, we present a robust modeling framework that considers disease transmissibility from the source through transport and dispersion and infectivity. The framework is designed to work across a range of particle sizes and estimate the generation rate, environmental fate, deposited dose, and infection, allowing for end-to-end analysis that can be transitioned to individual and population health models. In this paper, we perform sensitivity analysis on the model framework to demonstrate how it can be used to advance and prioritize research efforts by highlighting critical parameters for further analyses.

The effect of relative air humidity on the evaporation timescales of a human sneeze

The present paper investigates droplet and aerosol emission from the human respiratory function by numerical and experimental methods, which is analyzed at the worst-case scenario, a violent sneeze without a face covering. The research findings develop the understanding of airborne disease transmission relevant to COVID-19, its recent variants, and other airborne pathogens. A human sneeze is studied using a multiphase Computational Fluid Dynamics (CFD) model using detached eddy simulation coupled to the emission of droplets that break up, evaporate, and disperse. The model provides one of the first experimental benchmarks of CFD predictions of a human sneeze event. The experiments optically capture aerosols and droplets and are processed to provide spatiotemporal data to validate the CFD model. Under the context of large random uncertainty, the studies indicate the reasonable correlation of CFD prediction with experimental measurements using velocity profiles and exposure levels, indicating that the model captures the salient details relevant to pathogen dispersion. Second, the CFD model was extended to study the effect of relative humidity with respect to the Wells curve, providing additional insight into the complexities of evaporation and sedimentation characteristics in the context of turbulent and elevated humidity conditions associated with the sneeze. The CFD results indicated correlation with the Wells curve with additional insight into features, leading to non-conservative aspects associated with increased suspension time. These factors are found to be associated with the combination of evaporation and fluid-structure-induced suspension. This effect is studied for various ambient air humidity levels and peaks for lower humidity levels, indicating that the Wells curve may need a buffer in dry climates. Specifically, we find that the increased risk in dry climates may be up to 50% higher than would be predicted using the underlying assumptions in Wells' model.