Measuring stability of virus in aerosols under varying environmental conditions

Abstract

Methods Virus Strains and Culture MethodsSeventeen clone one (17Cl-1) mouse fibroblast cells (Sturman and Takemoto 1972) were cultured at 37 o C and 5% CO2 in Dulbecco's Modified Eagle Medium (DMEM, high glucose; Sigma, UK) supplemented with 10% foetal bovine serum (FBS, Sigma), 100 units/ml penicillin (Gibco, UK), 100 µg/ml streptomycin (Gibco, UK), non-essential amino acids (NEAA, Gibco), and L-glutamine (Gibco, UK). To generate MHV-A59 (Sawicki et al. 2005) viral stocks, T75 tissue culture flasks (Corning) seeded with 17CL-1 cells, were infected at a multiplicity of infection (MOI) of 0.01, and then incubated for 48 hours at 37 o C and 5% CO2. The virally infected cells were then subjected to a freeze-thaw cycle by placing the T75 flask into a -80 o C freezer overnight and then the culture thawed and centrifuged at 1200g before being aliquoted and stored at -80 o C. Airborne Longevity MeasurementsThe environmental conditions are set by adjusting the Peltier voltage and polarity to set the temperature and the ratio of dry to wet air to set the humidity. MHV suspension is drawn into a 1 ml syringe which is then attached to the instrument and used to feed the virus solution to the droplet dispenser via a remotely operated motor. The dispenser is remotely operated by computer and used to generate a population of droplets of the desired size within the electric field. Both the initial and final frequency of the electric field are set by computer as well as the rate at which the field frequency changes, to allow for the droplet to be kept within the trap as it equilibrates to the conditions. Once the desired time is reached, an isolation plate is retracted causing the electric field to be set to zero; then, the droplets are pulled down into a plate containing 5-10 ml of DMEM so that the remaining virus can be quantified. For each measurement, two levitations are carried out. First a short

The dynamics of SARS-CoV-2 infectivity with changes in aerosol microenvironment

“…( 14 ) Two further papers do not report sufficient information to estimate RSDs ( 15 , 16 ). The smaller RSD from the CELEBS is likely the result of the more stable environmental conditions, a more reproducible monodisperse droplet generation process, and improved methodology for viral infectivity quantification ( 39 ). Furthermore, CELEBS experiments are more straightforward to perform, allowing for more repeat measurements for each condition and leading to a high degree of confidence in the mean percentage infectivity values reported.…”

“…We have previously reported a unique approach to the study of infectious aerosol and the interplay between aerosol microphysics and pathogen survival, using complementary aerosol analysis techniques to assess the underlying mechanisms that govern the airborne longevity of pathogens ( 38 , 39 ). The aerosol stability of viruses and bacteria is investigated using the CELEBS (controlled electrodynamic levitation and extraction of bioaerosols onto a substrate) technique ( 38 – 40 ). In CELEBS ( SI Appendix , Fig.…”

Acidity of expiratory aerosols controls the infectivity of airborne influenza virus and SARS-CoV-2

“…This result confirms the importance of trace gases in determining the pH of indoor aerosol particles ( 24 ). If only CO 2 is considered, its volatilization from the particle would lead to an expected increase in pH after exhalation ( 31 ). Owing to aerosol acidification, rapid influenza virus inactivation occurs at ∼ 2 minutes, whereas SARS-CoV-2 (and the even more pH-tolerant HCoV-229E) remain infectious.…”

Nanofibers functionalized with surfactants to Eliminate SARS-CoV-2 and other airborne pathogens

“…Some become smaller, being more influenced by the airflow than gravity, making the droplet travel long distances (AYDIN et al, 2020;MORAWSKA et al, 2009), reaching distances greater than 3 m from its source (FENG et al, 2020). Some viruses can remain infective even after hours, especially in higher relative humidity (OSWIN et al, 2021).…”