(84aj) Persistence of Phi6, a Sars-Cov-2 Surrogate, in Simulated Indoor Environments: Effects of Humidity and Material Moisture Adsorption

The COVID-19 pandemic brought major challenges to public health and is primarily transmitted via aerosols, droplets, and fomites. However, there is a lack of understanding of virus persistence on fomites (i.e., building materials) under different environmental conditions in a realistic environment. Thus, we aimed to bridge this knowledge gap especially as fomites are a significant virus transmission route. This study utilized Pseudomonas Phage Phi6, an 85 nm enveloped dsRNA bacteria virus, as a coronavirus surrogate due to its structural similarities. The experiments were conducted in a 29 m³ full-scale aerobiology chamber to simulate a realistic indoor environment. The viral titers were quantified via virological Plaque Forming Assays (PFU) and molecular Reverse Transcription Quantitative Polymerase Chain Reaction (RT-qPCR), which quantify the infective viral load and total viral load respectively. We initially assessed the effect of our sampling methods on the viability and integrity of Phi6 to validate the observed relative humidity (RH)-induced inactivation. Our results show that the infectivity of Phi6 decreases by ≥ 1-log as the RH increases from 25% to 45% to 75% and then increases by ≥ 1-log as the RH increases to 85% both in air and when Phi6 is deposited on surfaces by gravitational settlement. The kinetics of RH-induced inactivation shows the decay rate of infectivity changed in the order (high to low) at 75% » 25% ≅ 45% ≅ 85%. In addition, we show that although material properties may impact virus persistence, local humidity at the air-substrate interface more significantly influences virus persistence on tested surfaces. These results provide more insights into viral transmission under varied environmental conditions with changes in the aerosol pH and how these changes affect the aerosolized virus. These findings will help the design of more effective strategies for viral control in indoor environments.