Unanswered questions on the airborne transmission of COVID-19.

Policies and measures to control pandemics are often failing. While biological factors controlling transmission are usually well explored, little is known about the environmental drivers of transmission and infection. For instance, respiratory droplets and aerosol particles are crucial vectors for the airborne transmission of the severe acute respiratory syndrome coronavirus 2, the causation agent of the coronavirus 2019 pandemic (COVID-19). Once expectorated, respiratory droplets interact with atmospheric particulates that influence the viability and transmission of the novel coronavirus, yet there is little knowledge on this process or its consequences on virus transmission and infection. Here we review the effects of atmospheric particulate properties, vortex zones, and air pollution on virus survivability and transmission. We found that particle size, chemical constituents, electrostatic charges, and the moisture content of airborne particles can have notable effects on virus transmission, with higher survival generally associated with larger particles, yet some viruses are better preserved on small particles. Some chemical constituents and surface-adsorbed chemical species may damage peptide bonds in viral proteins and impair virus stability. Electrostatic charges and water content of atmospheric particulates may affect the adherence of virion particles and possibly their viability. In addition, vortex zones and human thermal plumes are major environmental factors altering the aerodynamics of buoyant particles in air, which can strongly influence the transport of airborne particles and the transmission of associated viruses. Insights into these factors may provide explanations for the widely observed positive correlations between COVID-19 infection and mortality with air pollution, of which particulate matter is a common constituent that may have a central role in the airborne transmission of the novel coronavirus. Supplementary Information: The online version contains supplementary material available at 10.1007/s10311-022-01557-z.

Evaporation dynamics of a surrogate respiratory droplet in a vortical environment.

HYPOTHESIS: Vortex droplet interaction is crucial for understanding the route of disease transmission through expiratory jet where several such embedded droplets continuously interact with vortical structures of different strengths and sizes. EXPERIMENTS: A train of vortex rings with different vortex strength, quantified with vortex Reynolds number (Re'=0,53,221,297) are made to interact with an isolated levitated droplet, and the evolution dynamics is captured using shadowgraphy, particle image velocimetry (PIV), and backlight imaging technique. NaCl-DI water solution of 0, 1, 10 and 20 wt% concentrations are used as test fluids for the droplet. FINDINGS: The results show the dependence of evaporation characteristics on vortex strength, while the crystallization dynamics was found to be independent of it. A reduction of 12.23% and 14.6% in evaporation time was seen in case of de-ionized (DI) water and 1% wt NaCl solution respectively in presence of vortex ring train at Re'=221. In contrast to this, a minimal reduction in evaporation time (0.6% and 0.9% for DI water and 1% wt NaCl solution, respectively) is observed when Re' is increased from 221 to 297. The mechanisms for evaporation time reduction due to enhancement of convective heat and mass transfer from the droplet and shearing away of vapor layer by vortex ring interaction are discussed in this work.

Spirometer Based on Vortex Whistle to Monitor Lung Disorders

This paper describes a method to monitor lung disorders such as the sequelae of the novel coronavirus (SARS-CoV2) and asthma. A battery-less spirometer sensor element used in microphone-equipped devices such as smartphones was adopted. A vortex whistle was employed to measure the blowing flow rate and pressure. The physical characteristics of the vortex whistle sound frequency, blowing flow rate, blowing pressure, and sound pressure were theoretically clarified. Moreover, the structural conditions necessary to ensure a high performance of the whistle were experimentally derived, and the theoretically derived characteristics were experimentally validated using an actual whistle. The experimental results and theoretically derived characteristics were in agreement, and the sound frequency was noted to be linearly proportional to the flow rate. Furthermore, the sound pressure increased to +40 dB / decade as the frequency increased, and the outlet pressure was proportional to the square of the frequency. On the basis of these results, the signal processing conditions to acquire the information pertaining to the spirometer from the vortex sound were clarified. IEEE

Effect of not vortexing nasopharyngeal and throat swabs on SARS-CoV-2 nucleic acid detection: A pilot study.

The processing of swabs for respiratory virus detection involves vortexing while still in the viral transport medium (VTM). The effect of not vortexing swabs prior to analysis has not been studied extensively for SARS-CoV-2 detection, and presents an opportunity to improve pre-analytic laboratory workflow. We aimed to assess the impact of not vortexing nasopharyngeal/throat swabs submitted in VTM for SARS-CoV-2 testing. To assess the impact of not vortexing swabs, 277 swab samples were tested for SARS-CoV-2 RNA in paired vortexed and non-vortexed aliquots using eight routine nucleic acid amplification assays. We compared the qualitative (positive/negative) and semi-quantitative (cycle threshold, Ct) results. Following discordant analysis, all but one non-vortexed sample had the same qualitative result as the vortexed sample. 27.4 % of samples were SARS-CoV-2 positive. Comparison of Ct values revealed an apparent reduction in human cellular nucleic acid in the non-vortexed samples (mean Ct values of 24.0 and 26.5 for vortexed and non-vortexed samples, respectively, p < 0.0001) and increased Ct values for non-vortexed samples using a laboratory-developed SARS-CoV-2 assay (mean Ct values of 4.1 and 4.2 for vortexed and non-vortexed samples, respectively; p < 0.0001), but this was not observed for a more automated commercial SARS-CoV-2 assay (mean Ct values of 15.2 for both vortexed and non-vortexed samples, respectively; p = 0.68). While vortexing swabs appears to improve the recovery of cellular material, it does not have an appreciable impact on the qualitative sensitivity of SARS-CoV-2 nucleic acid tests, which may support omission of this step and simplification of front-end sample processing.