Establishing a universal model virus system for breath air aerosol studies, including an appropriate sampling system

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As stated already in the call, there is a significant lack of reliable data on dispersion, aging, and deposition of Breath Air Aerosol (BAA) carrying viruses. One main reason for this shortcoming is the limited comparability of the numerous studies in the field, which again is caused by the fact that these studies are carried out with a wide range of different particle systems. Some physical properties of BAA can be simulated by polystyrol latex particles, other by nebulizing bacteriophages. These particle systems are only suitable to simulate particle behavior after release. The release process by the human respiratory tract, which is responsible for the distribution of viruses in various (size) fractions and number densities inside BAA particles, is not accessible. However, the release conditions are responsible for the further fate of the particles, such as drying, aging, sedimentation, but also for the infectivity of the enclosed viruses. These effects can only be assessed by clinical tests with patients (e.g. influence or COVID-19 patients), implicating significant health risk as well as a considerable health burden for the patient.The aim of this project is to establish the TT-virus as non-infectious, universal model virus system for studies on viruses in Breath Air Aerosol. The TT virus, named after the initials of the first patient, where it was detected, is a genus of non-enveloped viruses in the family Anelloviridae. Depending on the world region, between 10 and more than 90% of all adults carry this virus, which is considered not to cause any negative health effects. As the TT virus is also contained in the respiratory tract and in BAA, it might be an ideal model organism. The presence of TT viruses in different BAA size fractions will be investigated by means of various sampling and measuring devices, breath air sampling chambers, masks, and helmets available in our labs. Another challenge in virus-carrying aerosol sampling is the low sampling efficiency, particularly when the infectivity of the sampled viruses is to be maintained. Hence, in parallel to the basic investigations on TT viruses on breath air aerosol, a novel sampling device, comprising a water condensation chamber and an impinger, will be constructed to sample viruses contained in BAA with high efficiency and, equally important, in a way that the infectivity is maintained and accessible for further tests.