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1.
Viruses ; 14(4):684, 2022.
Article in English | MDPI | ID: covidwho-1762725

ABSTRACT

Recent research using UV radiation with wavelengths in the 200–235 nm range, often referred to as far-UVC, suggests that the minimal health hazard associated with these wavelengths will allow direct use of far-UVC radiation within occupied indoor spaces to provide continuous disinfection. Earlier experimental studies estimated the susceptibility of airborne human coronavirus OC43 exposed to 222-nm radiation based on fitting an exponential dose–response curve to the data. The current study extends the results to a wider range of doses of 222 nm far-UVC radiation and uses a computational model coupling radiation transport and computational fluid dynamics to improve dosimetry estimates. The new results suggest that the inactivation of human coronavirus OC43 within our exposure system is better described using a bi-exponential dose–response relation, and the estimated susceptibility constant at low doses-the relevant parameter for realistic low dose rate exposures-was 12.4 ±0.4 cm2/mJ, which described the behavior of 99.7% ±0.05% of the virus population. This new estimate is more than double the earlier susceptibility constant estimates that were based on a single-exponential dose response. These new results offer further evidence as to the efficacy of far-UVC to inactivate airborne pathogens.

2.
Sci Rep ; 11(1): 19930, 2021 10 07.
Article in English | MEDLINE | ID: covidwho-1462026

ABSTRACT

Transmission of SARS-CoV-2 by aerosols has played a significant role in the rapid spread of COVID-19 across the globe. Indoor environments with inadequate ventilation pose a serious infection risk. Whilst vaccines suppress transmission, they are not 100% effective and the risk from variants and new viruses always remains. Consequently, many efforts have focused on ways to disinfect air. One such method involves use of minimally hazardous 222 nm far-UVC light. Whilst a small number of controlled experimental studies have been conducted, determining the efficacy of this approach is difficult because chamber or room geometry, and the air flow within them, influences both far-UVC illumination and aerosol dwell times. Fortunately, computational multiphysics modelling allows the inadequacy of dose-averaged assessment of viral inactivation to be overcome in these complex situations. This article presents the first validation of the WYVERN radiation-CFD code for far-UVC air-disinfection against survival fraction measurements, and the first measurement-informed modelling approach to estimating far-UVC susceptibility of viruses in air. As well as demonstrating the reliability of the code, at circa 70% higher, our findings indicate that aerosolized human coronaviruses are significantly more susceptible to far-UVC than previously thought.


Subject(s)
Coronavirus 229E, Human/radiation effects , Coronavirus Infections/prevention & control , Coronavirus OC43, Human/radiation effects , Disinfection/methods , Ultraviolet Rays , Virus Inactivation/radiation effects , Aerosols/isolation & purification , Air Microbiology , COVID-19/prevention & control , Computer Simulation , Coronavirus 229E, Human/isolation & purification , Coronavirus 229E, Human/physiology , Coronavirus OC43, Human/isolation & purification , Coronavirus OC43, Human/physiology , Disinfection/instrumentation , Equipment Design , Humans , Models, Biological
3.
Sci Rep ; 10(1): 19659, 2020 11 12.
Article in English | MEDLINE | ID: covidwho-922273

ABSTRACT

There are increased risks of contracting COVID-19 in hospitals and long-term care facilities, particularly for vulnerable groups. In these environments aerosolised coronavirus released through breathing increases the chance of spreading the disease. To reduce aerosol transmissions, the use of low dose far-UVC lighting to disinfect in-room air has been proposed. Unlike typical UVC, which has been used to kill microorganisms for decades but is carcinogenic and cataractogenic, recent evidence has shown that far-UVC is safe to use around humans. A high-fidelity, fully-coupled radiation transport and fluid dynamics model has been developed to quantify disinfection rates within a typical ventilated room. The model shows that disinfection rates are increased by a further 50-85% when using far-UVC within currently recommended exposure levels compared to the room's  ventilation alone. With these magnitudes of reduction, far-UVC lighting could be employed to mitigate SARS-CoV-2 transmission before the onset of future waves, or the start of winter when risks of infection are higher. This is particularly significant in poorly-ventilated spaces where other means of reduction are not practical, in addition social distancing can be reduced without increasing the risk.


Subject(s)
COVID-19/transmission , Disinfection/methods , SARS-CoV-2/radiation effects , Ultraviolet Rays , Air Conditioning , COVID-19/epidemiology , Disinfection/standards , Humans , Models, Statistical , Ventilation
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