A Micronized Electrostatic Precipitator Respirator Effectively Removes Ambient SARS-CoV-2 Bioaerosols

RationaleInhalation of ambient SARS-CoV-2-containing bioaerosols leads to infection and pandemic airborne transmission in susceptible populations. Filter-based respirators effectively reduce exposure but complicate normal respiration through breathing zone pressure differential and are therefore impractical for long-term use. ObjectivesWe tested the comparative effectiveness of a prototyped micronized electrostatic precipitator (mEP) to a filter-based respirator (N95) in the removal of viral bioaerosols from a simulated inspired air stream. MethodsEach respirator was tested within a 16-liter environmental chamber housed within a Class III biological safety cabinet within biosafety level 3 containment. SARS-CoV-2 containing bioaerosols were generated into the chamber, drawn by vacuum through each respirator, and physical particle removal and viral genomic RNA were measured distal to the breathing zone of each device. Measurement and Main ResultsThe mEP respirator removed particles (96.5{+/-}0.4%) approximating efficiencies of the N95 (96.9{+/-}0.6%). The mEP respirator similarly decreased SARS-CoV-2 viral RNA (99.792%) when compared to N95 removal (99.942%) as a function of particle removal from the airstream distal to the breathing zone of each respirator. ConclusionsThe mEP respirator approximated performance of a filter-based N95 respirator for particle removal and viral RNA as a constituent of the SARS-CoV-2 bioaerosols generated for this evaluation. In practice, the mEP respirator would provide equivalent protection from ambient infectious bioaerosols as the N95 respirator without undue pressure drop to the wearer, thereby facilitating long-term use in an unobstructed breathing configuration.

Myeloid cell-driven nonregenerative pulmonary scarring is conserved in multiple nonhuman primate species regardless of SARS-CoV-2 infection modality

The novel coronavirus SARS-CoV-2 has caused a worldwide pandemic resulting in widespread efforts in development of animal models that recapitulate human disease for evaluation of medical countermeasures, and to dissect COVID-19 immunopathogenesis. We tested whether route of experimental infection substantially changes COVID-19 disease characteristics in two species (Macaca mulatta; rhesus macaques; RM, Chlorocebus atheiops; African green monkeys; AGM) of nonhuman primates. Species-specific cohorts of RM and AGM Rhesus macaques (Macaca mulatta, RMs) and African green monkeys (Chlorocebus aethiops, AGMs) were experimentally infected with homologous SARS-CoV-2 by either direct mucosal instillation or small particle aerosol in route-discrete subcohorts. Both species demonstrated equivalent infection initially by either exposure route although the magnitude and duration of viral loading was greater in AGMs than that of the RM. Clinical onset was nearly immediate (+1dpi) in mucosally-exposed cohorts whereas aerosol-infected animals began to show signs +7dpi. Myeloid cell responses indicative of the development of pulmonary scarring and extended lack of regenerative capacity in the pulmonary compartment was a conserved pathologic response in both species by either exposure modality. This pathological commonality may be useful in future anti-fibrosis therapeutic evaluations and expands our understanding of how SARS-CoV-2 infection leads to ARDS and functional lung damage.

Exhaled aerosol increases with COVID-19 infection, and risk factors of disease symptom severity

Coronavirus disease-19 (COVID-19) transmits by droplets generated from surfaces of airway mucus during processes of respiration within hosts infected by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) virus. We studied respiratory droplet generation and exhalation in human and nonhuman primate subjects with and without COVID-19 infection to explore whether SARS-CoV-2 infection, and other changes in physiological state, translates into observable evolution of numbers and sizes of exhaled respiratory droplets in healthy and diseased subjects. In our observational cohort study of the exhaled breath particles of 74 healthy human subjects, and in our experimental infection study of eight nonhuman primates infected by aerosol with SARS-CoV-2, we found that exhaled aerosol particles increase one to three orders of magnitude with aging, high BMI, and COVID-19 infection. These variances appear to be related to changes in airway mucus surface composition and the propensity for mucus surfaces to breakup into small droplets during acts of breathing. We also observed that 20% of those participating in our human study accounted for 80% of the overall exhaled bioaerosol, reflecting a bioaerosol distribution analogous to a classical 20:80 super spreader distribution.