Evaluation of Viral Inactivation on Dry Surface by High Peak Power Microwave (HPPM) Exposure.

Previous research has shown that virus infectivity can be dramatically reduced by radio frequency exposure in the gigahertz (GHz) frequency range. Given the worldwide SARS-CoV-2 pandemic, which has caused over 1 million deaths and has had a profound global economic impact, there is a need for a noninvasive technology that can reduce the transmission of virus among humans. RF is a potential wide area-of-effect viral decontamination technology that could be used in hospital rooms where patients are expelling virus, in grocery and convenience stores where local populations mix, and in first responder settings where rapid medical response spans many potentially infected locations within hours. In this study, we used bovine coronavirus (BCoV) as a surrogate of SARS-CoV-2 and exposed it to high peak power microwave (HPPM) pulses at four narrowband frequencies: 2.8, 5.6, 8.5, and 9.3 GHz. Exposures consisted of 2 µs pulses delivered at 500 Hz, with pulse counts varied by decades between 1 and 10,000. The peak field intensities (i.e. the instantaneous power density of each pulse) ranged between 0.6 and 6.5 MW/m2 , depending on the microwave frequency. The HPPM exposures were delivered to plastic coverslips containing BCoV dried on the surface. Hemagglutination (HA) and cytopathic effect analyses were performed 6 days after inoculation of host cells to assess viral infectivity. No change in viral infectivity was seen with increasing dose (pulse number) across the tested frequencies. Under all conditions tested, exposure did not reduce infectivity more than 1.0 log10. For the conditions studied, high peak power pulsed RF exposures in the 2-10 GHz range appear ineffective as a virucidal approach for hard surface decontamination. © 2023 Bioelectromagnetics Society.

Mathematical modeling of the dynamics of COVID-19 variants of concern: Asymptotic and finite-time perspectives.

The COVID-19 pandemic has seen multiple waves, in part due to the implementation and relaxation of social distancing measures by the public health authorities around the world, and also caused by the emergence of new variants of concern (VOCs) of the SARS-Cov-2 virus. As the COVID-19 pandemic is expected to transition into an endemic state, how to manage outbreaks caused by newly emerging VOCs has become one of the primary public health issues. Using mathematical modeling tools, we investigated the dynamics of VOCs, both in a general theoretical framework and based on observations from public health data of past COVID-19 waves, with the objective of understanding key factors that determine the dominance and coexistence of VOCs. Our results show that the transmissibility advantage of a new VOC is a main factor for it to become dominant. Additionally, our modeling study indicates that the initial number of people infected with the new VOC plays an important role in determining the size of the epidemic. Our results also support the evidence that public health measures targeting the newly emerging VOC taken in the early phase of its spread can limit the size of the epidemic caused by the new VOC (Wu et al., 2139Wu, Scarabel, Majeed, Bragazzi, & Orbinski, ; Wu et al., 2021).

Maintenance of bronchoscopy services during the covid-19 pandemic: Experience from a Tertiary care centre

Bronchoscopy is an aerosol-generating procedure (AGP) and the COVID-19 pandemic has necessitated changes in provision of our service. This retrospective analysis reviews our institutional response to maintaining safe and efficient bronchoscopy services throughout the COVID-19 pandemic. Aim To analyse changes in numbers of and indications for flexible bronchoscopy (FB) and endobronchial ultrasound (EBUS) between December 2019-August 2020, and the mitigating measures introduced by our centre to keep the service operating. Method Data was pulled from our procedure database for the three months pre-COVID-19 (December 2019-February 2020), the COVID peak (March to May 2020) and the 'recovery' phase (June-mid August 2020). Patient records were analysed for the indication for procedure and diagnosis. Cancelled procedures and research bronchoscopies were excluded. Results 433 procedures were undertaken during the study period. Figure 1 shows the number of endoscopic procedures by indication and procedure type. There was an overall decrease in procedures during the pandemic, with predominantly EBUS cancer procedures being undertaken. The number of cancer cases performed across all three periods was comparable. Pre-procedure COVID swabs became mandatory in our institution from 29th April 2020. Of 167 cases, two were postponed (1 positive test and 1 febrile patient on procedure day). No patients were cancelled during pre-procedural telephone COVID-19 screening. Discussion Bronchoscopy procedures declined during the COVID-19 pandemic. However, our service maintained 4 lists per week during the peak with reinstatement of six lists during the COVID-endemic period. Bronchoscopy training was maintained with all lists having an assigned trainee. AGPrelated air exchange protocols limited the number of procedures per list and elective procedures were postponed early in the pandemic. Our centre had a proactive approach to running the service, introducing mandatory pre-procedure COVID swabbing early together with telephone screening pre-BTS guidance. Staff safety was prioritised via universal use of powered airpurifying respiratory (PAPR) use which eliminated the need for mask-fit testing and seeking FFP3 mask availability. It is feasible to maintain a safe and efficient bronchoscopy service in the midst of a pandemic with the implementation of appropriate pathways and provision of adequate personal protective equipment.

P29 Maintenance of bronchoscopy services during the COVID-19 pandemic: Experience from a tertiary care centre

P29 Figure 1DiscussionBronchoscopy procedures declined during the COVID-19 pandemic. However, our service maintained 4 lists per week during the peak with reinstatement of six lists during the COVID-endemic period. Bronchoscopy training was maintained with all lists having an assigned trainee. AGP-related air exchange protocols limited the number of procedures per list and elective procedures were postponed early in the pandemic.Our centre had a proactive approach to running the service, introducing mandatory pre-procedure COVID swabbing early together with telephone screening pre-BTS guidance. Staff safety was prioritised via universal use of powered air-purifying respiratory (PAPR) use which eliminated the need for mask-fit testing and seeking FFP3 mask availability.It is feasible to maintain a safe and efficient bronchoscopy service in the midst of a pandemic with the implementation of appropriate pathways and provision of adequate personal protective equipment.

Why is it difficult to accurately predict the COVID-19 epidemic?

Since the COVID-19 outbreak in Wuhan City in December of 2019, numerous model predictions on the COVID-19 epidemics in Wuhan and other parts of China have been reported. These model predictions have shown a wide range of variations. In our study, we demonstrate that nonidentifiability in model calibrations using the confirmed-case data is the main reason for such wide variations. Using the Akaike Information Criterion (AIC) for model selection, we show that an SIR model performs much better than an SEIR model in representing the information contained in the confirmed-case data. This indicates that predictions using more complex models may not be more reliable compared to using a simpler model. We present our model predictions for the COVID-19 epidemic in Wuhan after the lockdown and quarantine of the city on January 23, 2020. We also report our results of modeling the impacts of the strict quarantine measures undertaken in the city after February 7 on the time course of the epidemic, and modeling the potential of a second outbreak after the return-to-work in the city.