Biocascade inlet - Project Summary Respiratory infections are the most common reason for doctor visits and the third leading cause of deaths. Viruses are the causative agents of most respiratory tract infections. Knowledge of the transmission modes for pathogenic respiratory viruses is critical for improving mitigation strategies that safeguard public health, but understanding their transmission mechanisms is hampered by existing sampling methods. So far, no method has been recommended by the public health organizations for the collection and detection of airborne viruses. The lack of standard protocols results from the fact that no sampling procedure is appropriate for sampling of all bioaerosols. During sampling, it is necessary to minimize inactivation of microbes, such as incapacitating desiccation and destructive impaction upon collection onto a collection surface. When collecting samples for detection of viral genomic RNA or DNA, maintaining the viability of the virus is not necessary, but maintaining nucleic acid integrity is essential, especially for RNA, which is rapidly degraded upon exposure to the environment. For assessing infectivity, the pathogen needs to be viable. In both cases, gentle collection methods are required. Although previous efforts have tried to separate virus-containing particles by aerodynamic size, maintaining their infectivity during sampling remains challenging. Here, we aim to develop a novel sampling system, the BioCascade, that will allow the collection of airborne viruses within four different bioaerosol particle size-fractions: >10 um, PM4-10, PM1.5-4 and PM1.5 into liquid medium, while maintaining infectivity of the viruses that are collected. In Phase I, we built a BioCascade prototype. Its particle size-range cut-off and the collection efficiency of each stage were modeled and designed by numerical simulations followed by validation through laboratory experiments using National Institutes of Science and Technology (NIST)-certified standard- sized particles. Its ability to collect and maintain the infectivity of bioaerosol was then assessed using microorganisms that were representative of the size ranges that would be encountered in bioaerosols. All Phase-I aims were successfully achieved. In Phase II, we aim to improve our prototype by expanding its capabilities, such as a cold collection chamber for providing a better environment for the collected pathogens, and a control system to maintain the liquid level that enables increased sampling time to several hours. By providing size-fractionated air samples that contain infectious pathogens, the Biocascade is envisioned as a powerful tool, not available before, that can transform our current disease-control paradigm from a reactive approach (to an outbreak after its fact) to a proactive approach (inform us the forthcoming viruses).
