Evaluation of 4.0 GHz RF Exposure Effects on Bioaerosols Containing Bovine Coronavirus

This study investigates the interaction between 4.0 GHz microwave radiation and bovine coronavirus (BCoV). Previous work by the authors at 5.6 GHz demonstrated mild (~74%) but statistically significant reductions in virus survival, attributed to a combination of thermal as well as non-thermal effects, such as Structure-Resonant Energy Transfer (SRET). This research aims to expand the frequency dataset to better elucidate the roles of thermal and non-thermal effects in radio frequency (RF)-induced viral inactivation. These experiments were performed in a waveguide containing a flowing aerosol stream and were limited to a single RF waveform: ∼2 μs square envelope, 4.0 GHz, 4.8 kHz repetition rate. Aerosol streams were exposed to RF electric field amplitudes in the range of 41.5 ± 5.2 kV/m. Under laminar flow conditions, 80% of the total collected aerosol stream spends 1.0 s or less in the RF exposure region. Analysis via TCID₅₀ assays revealed no statistically significant reduction in virus survival compared to controls, nor significant changes in data variance or standard deviation. Results align with prior observations that higher frequencies (~7-8 GHz) produce more pronounced inactivation effects, while lower frequencies exhibit reduced efficacy. The findings underscore the frequency dependence of microwave inactivation mechanisms and highlight the need for further studies at higher frequencies. Bioelectromagnetics. 00:00-00, 2025. © 2025 Bioelectromagnetics Society.