Shielding of Viruses such as SARS-CoV-2 from Ultraviolet Radiation in Particles Generated by Sneezing or Coughing: Numerical Simulations of Survival Fractions

Shielding of Viruses such as SARS-CoV-2 from Ultraviolet Radiation in Particles Generated by Sneezing or Coughing: Numerical Simulations of Survival Fractions Steven C. Hill, David C. Doughty, and Daniel W. Mackowski DEVCOM Army Research Laboratory, 2800 Powder Mill Rd., Adelphi, Maryland, USA (Hill and Doughty); Auburn University, Auburn, Alabama, USA (Mackowski) #Address correspondence to Steve Hill, [email protected] ABSTRACT SARS-CoV-2 and other microbes within aerosol particles can be partially shielded from UV radiation. The particles refract and absorb light, and thereby reduce the UV intensity at various locations within the particle. Shielding has been demonstrated in calculations of UV intensities within spherical approximations of SARS-CoV-2 virions that are within spherical particles approximating dried-to-equilibrium respiratory fluids. The purpose of this paper is to calculate the survival fractions of virions (i.e., the fractions of virions that can infect cells) within spherical particles approximating dried respiratory fluids, and to investigate the implications of these calculations for using UV light for disinfection. The particles may be on a surface or in air. In this paper the survival fraction (S) of a set of virions illuminated with a UV fluence (F, in J/m2) is approximated as S=exp(-kF), where k is the UV inactivation rate constant (m2/J). The average survival fractions (Sp) of all the simulated virions in a particle are calculated using the calculated decreases in fluence. The results show that virions in particles of dried respiratory fluids can have significantly larger Sp than do individual virions. For individual virions, and virions in 1, 5, and 9 µm particles illuminated (normal incidence) on a surface with 260-nm UV light, the Sp = 0.00005, 0.0155, 0.22 and 0.28, respectively, when kF=10. The Sp decrease to <10-7, <10-7, 0.077 and 0.15, respectively, for kF=100. Calculated results also show that illuminating particles with UV beams from widely separated directions can strongly reduce the Sp. These results suggest that the size distributions and optical properties of the dried particles of virion-containing respiratory fluids are likely important in effectively designing and using UV germicidal irradiation systems for microbes in particles. The results suggest the use of reflective surfaces to increase the angles of illumination and decrease the Sp. The results suggest the need for measurements of the Sp of SARS-CoV-2 in particles having compositions and sizes relevant to the modes of disease transmission.

Report on the Thirty-Second International Florida Artificial Intelligence Research Society Conference (FLAIRS-32)

The Thirty-Second International Florida Artificial Intelligence Research Society Conference was held May 19–22, 2019, at the Lido Beach Resort in Sarasota, Florida, USA. The conference events included tutorials, invited speakers, special tracks, and presentations of papers, posters, and awards. The conference chair was Vasile Rus from the University of Memphis. The program cochairs were Keith Brawner from the Army Research Laboratory and Roman Barták from Charles University, Prague. The special tracks were coordinated by Eric Bell.

Report on the Thirty-First International Florida Artificial Intelligence Research Society Conference (FLAIRS-31)

The Thirty-First International Florida Artificial Intelligence Research Society Conference (FLAIRS-31) was held May 21-23, 2018, at the Crowne Plaza Oceanfront in Melbourne, Florida, USA. The conference events included invited speakers, special tracks, and presentations of papers, posters, and awards. The conference chair was Zdravko Markov from Central Connecticut State University. The program co-chairs were Vasile Rus from the University of Memphis and Keith Brawner from the Army Research Laboratory. The special tracks were coordinated by Roman Barták from Charles University in Prague.