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. Previously, we demonstrated shielding in calculations of UV intensities within spherical approximations of SARS-CoV-2 virions within spherical particles approximating dried-to-equilibrium respiratory fluids. The purpose of this paper is to extend that work to survival fractions of virions (i.e., 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. Here, the survival fraction (S) of a set of individual virions illuminated with a UV fluence (F, in J/m²) is assumed described by S(kF) = exp(-kF), where k is the UV inactivation rate constant (m²/J). The average survival fraction (S_p) of the simulated virions in a group of particles is calculated using the energy absorbed by each virion in the particles. The results show that virions within particles of dried respiratory fluids can have larger S_p than do individual virions. For individual virions, and virions within 1-, 5-, and 9-µm particles illuminated (normal incidence) on a surface with 260-nm UV light, the S_p = 0.00005, 0.0155, 0.22, and 0.28, respectively, when kF = 10. The S_p decrease to <10⁻⁷, <10⁻⁷, 0.077, and 0.15, respectively, for kF = 100. Results also show that illuminating particles with UV beams from widely separated directions can strongly reduce the S_p. These results suggest that the size distributions and optical properties of the dried particles of virion-containing respiratory fluids are likely important to 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 S_p. The results suggest the need for measurements of the S_p of SARS-CoV-2 in particles having compositions and sizes relevant to the modes of disease transmission.

摘要

SARS-CoV-2 和气溶胶颗粒中的其他微生物可以部分屏蔽紫外线辐射。颗粒折射和吸收光，从而降低颗粒内不同位置的紫外线强度。此前，我们在近似干燥至平衡呼吸液的球形颗粒内，在计算 SARS-CoV-2 病毒粒子的球形近似值内的紫外线强度时证明了屏蔽。本文的目的是将这项工作扩展到近似干燥呼吸道液体的球形颗粒内病毒粒子的存活分数（即可以感染细胞的病毒粒子分数），并研究这些计算对使用紫外线消毒的影响。颗粒可以在表面上或在空气中。这里，生存分数（S) 用 UV 能量密度 ( F，单位 J/m ² )照射的一组单个病毒粒子的) 假设为S ( kF ) = exp( -kF )，其中k是 UV 灭活速率常数 (m ² /J) . 平均存活分数（小号_p的一组颗粒在模拟的病毒体）是使用由在每个颗粒病毒体所吸收的能量来计算。结果表明，干燥的呼吸道液颗粒内的病毒粒子可以具有更大的S _p而不是单个病毒。对于单个病毒粒子以及 1、5 和 9 µm 粒子在 260 nm 紫外光表面照射（法向入射）内的病毒粒子，当kF时，S _p分别为0.00005、0.0155、0.22和 0.28 =  10。对于kF  = 100 ，S _{p 分别}降低到 <10 ^-7、<10 ^-7、0.077 和 0.15 。结果还表明，用来自广泛分离方向的紫外线光束照射粒子可以大大降低S _p. 这些结果表明，含有病毒粒子的呼吸液的干燥颗粒的尺寸分布和光学特性对于有效设计和使用用于颗粒中微生物的紫外线杀菌照射系统可能很重要。结果表明使用反射面来增加照明角度并降低S _p。结果表明，需要测量具有与疾病传播模式相关的成分和大小的颗粒中 SARS-CoV-2的S _p。