Aerosol Science Meets Virology
Contact Persons: Liviana Klein, Nir Bluvshtein, Ulrich Krieger, Beiping Luo and Thomas Peter
Respiratory illnesses like the seasonal influenza or the current COVID-19 pandemic can cause several hundred thousand of deaths each year. In the transmission of SARS-CoV-2 and influenza viruses, expiratory aerosol particles can play an essential role. However, a full understanding of the fundamental mechanism is still missing. To gain a better understanding, an interdisciplinary approach is needed.
Our research group of atmospheric chemistry with sound knowledge of aerosol science wants to bridge the gap between disciplines and is heading for new shores. In collaboration with the Molecular Virology group of UZH (Prof. Silke Stertz) and Environmental Chemistry & Engineering groups at EPFL (Prof. Tamar Kohn, Prof. Athanasios Nenes), two research projects are being realized:
1. “Infectivity of influenza viruses in expiratory aerosols under ambient temperatures and humidity” (IVEA)
2. “Acidic pH inactivation of SARS‐CoV‐2 in exhaled breath and expectoration” (ApHiCoV).
In the IVEA project, we want to determine how relative humidity and temperature control the physico-chemical properties of expiratory aerosol particles, and how these in turn affect influenza virus infectivity. While in the ApiHiCoV project, we examine the impact of acidification on the infectivity of SARS-CoV-2.
What are expiratory aerosol particles and why are they important?
It is commonly known that sneezing and coughing produce droplets, however, also speaking, or even just breathing, generates aerosol particles which can stay aloft for a long period of time.
Expiratory aerosol particles consist of air lining fluid or saliva which cover our respiratory tract or mouth. The amount and size of generated aerosol particles depend on how loud you speak, what you say, or how deep you breath. If you are infected with a respiratory virus (e.g. influenza, SARS-CoV-2), these exhaled particles can contain infectious virions.
Why might ambient conditions be important for the infectivity of viruses?
Ambient temperature and humidity might impact the properties of expiratory particles which in turn might affect the infectivity of the virions within the particles. During exhalation, the particle can undergo a fast change from higher humidity and temperature to lower humidity and temperature in the ambient air. The subsequent drying of the particles will change its salt concentration and water activity. Also, the pH value can change due to evaporation of ammonia and water. All these processes might influence the infectivity of the virions.
We plan to use the following techniques to investigate the expiratory aerosol particles:
• With the Electrodynamic Balance (EDB), we can characterize properties of air lining fluid and saliva particles such as hygroscopic growth, refractive index, phase transitions, and water diffusivity.
• Using microscopy with a climate chamber, we investigate the behavior of air lining fluid and saliva droplets under varying temperatures and humidity to observe phase separation and crystallization. In addition, we plan to locate the virions within the droplets.
• With Raman spectroscopy, we characterize the composition of respiratory fluids.
• Physico-chemical modeling enables the prediction of the spatiotemporal range of aerosol transmission pathways.