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We review recent results on the formation and evolution of aqueous organic aerosols via concurrent nucleation/condensation and chemical aging processe…

****!!!!*** {Also see citing documents at agupubs.onlinelibrary.wiley.com/doi/10.1029/RG021i004p00903} "organic films... If present, they will increase the lifetimes of aerosol particles... both by inhibiting water vapor evaporation and by reducing the efficiency with which these atmospheric components are scavenged. The presence of the films will not cause a significant reduction of solar radiation within the aqueous solution. It appears likely, however, that the transport of gaseous molecules into and out of the aqueous solution will be impeded by factors of several hundred or more when organic films are present. Since incorporated gas molecules provide much of the oxidizing potential of atmospheric water droplets, the organic films will play a major role in droplet chemistry by strongly inhibiting solution oxidation"

"Airborne transmission arises through the inhalation of aerosol droplets exhaled by an infected person and is now thought to be the primary transmission route of COVID-19. By assuming that the respiratory droplets are mixed uniformly through an indoor space, we derive a simple safety guideline for mitigating airborne transmission that would impose an upper bound on the product of the number of occupants and their time spent in a room. Our theoretical model quantifies the extent to which transmission risk is reduced in large rooms with high air exchange rates, increased for more vigorous respiratory activities, and dramatically reduced by the use of face masks. Consideration of a number of outbreaks yields self-consistent estimates for the infectiousness of the new coronavirus."

Dec 2020. *****!!!!!****!!!*** We find SARS-CoV-2 survives longest at low temperatures and extreme relative humidities; median estimated virus half-life is over 24 hours at 10 °C and 40 % RH, but approximately 1.5 hours at 27 °C and 65 % RH."

***!!!!******!!!!!***** "We investigated the effects of RH on the viability of bacteria and viruses in both suspended aerosols and stationary droplets using traditional culture-based approaches. Results showed that viability of bacteria generally decreased with decreasing RH. Viruses survived well at RHs lower than 33% and at 100%, whereas their viability was reduced at intermediate RHs. We then explored the evaporation rate of droplets consisting of culture media and the resulting changes in solute concentrations over time; as water evaporates from the droplets, solutes such as sodium chloride in the media become more concentrated. Based on the results, we suggest that inactivation of bacteria is influenced by osmotic pressure resulting from elevated concentrations of salts as droplets evaporate. We propose that the inactivation of viruses is governed by the cumulative dose of solutes or the product of concentration and time, as in disinfection kinetics."

On March 17, 2020, a member of a Skagit County, Washington, choir informed Skagit County Public Health (SCPH) that several members of the 122-member choir had become ill.

An employee at a hospital in San Jose wore an “air-powered” costume on Christmas. Within days, 44 staff members had tested positive for the coronavirus and one had died, the hospital said.

COVID-19 is spread by aerosols - a review of the available science.

There is mounting evidence that the aerosol transmission route plays a significant role in the spread of influenza in temperate regions and that the efficiency of this route depends on humidity. Nevertheless, the precise mechanisms by which humidity might influence transmissibility via the aerosol r …

Aug 2020.

We provide evidence of a mode of transmission seldom considered for influenza: airborne virus transport on microscopic particles called “aerosolized fomites.” In the guinea pig model of influenza virus transmission, we show that the airborne particulates produced by infected animals are mainly non-respiratory in origin. Surprisingly, we find that an uninfected, virus-immune guinea pig whose body is contaminated with influenza virus can transmit the virus through the air to a susceptible partner in a separate cage. We further demonstrate that aerosolized fomites can be generated from inanimate objects, such as by manually rubbing a paper tissue contaminated with influenza virus. Our data suggest that aerosolized fomites may contribute to influenza virus transmission in animal models of human influenza, if not among humans themselves, with important but understudied implications for public health.

Influenza viruses can spread through the air on dust, fibers and other microscopic particles, according to new research from the University of California, Davis, and the Icahn School of Medicine at

"Large floor fans create a focused blast that pushes air and the virus a long way. A number of studies show you can get infected at a good distance because of those large fans, Tuznik said."

Also-- Coronavirus protection: How masks might stop the spread through coughs

"SARS-CoV-2 was also found to be transmitted via the air in two out of six ferrets21, and in two out of six cats. However, only low levels of SARS-CoV-2 RNA were detected in nasal washes and feces of the indirect recipient ferrets, and no infectious virus was isolated21. Furthermore, virus shedding was shorter as compared to the donor animals and only one out of the two SARS-CoV-2 RNA positive indirect recipient ferrets seroconverted. Similarly, the transmission via the air between cats was not efficient. " "No SARS-CoV-2 RNA was detected in the air sampled in three isolation rooms, or 10 cm from a symptomatic patient who was breathing, coughing or speaking. Nevertheless, RNA was detected on the air exhaust outlet of one of the isolation rooms in the first study, suggesting that virus-laden droplets may be displaced by airflows."

April 2020

Patients with respiratory manifestations of COVID-19 produce aerosols in the absence of aerosol-generating procedures that contain viable SARS-CoV-2, and these aerosols may serve as a source of transmission of the virus.

"People infected with SARS-CoV-2 exhaled 1,000–100,000 copies per minute of viral RNA, a marker of the pathogen’s presence. Because the volunteers simply breathed out, the viral RNA was probably carried in aerosols." "When researchers created aerosols of the new coronavirus, the aerosols remained infectious for at least 16 hours, and had greater infectivity than did those of the coronaviruses SARS-CoV and MERS-CoV." "No amount of ventilation could have reduced the risk to an acceptable level for the two-and-a-half-hour rehearsal, she says." "SARS-CoV-2 in mock saliva aerosols lost 90% of its viability in 6 minutes of exposure to summer sunlight, compared with 125 minutes in darkness."

CDC provides credible COVID-19 health information to the U.S.

Many of the sharpest increases per capita over the past week came in states like Wisconsin, Utah, Iowa and the Dakotas.

Most spread the virus to only a few people — or none at all. But a small percentage transmit it with alarming efficiency, studies show.

There is overwhelming evidence that inhalation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) represents a major transmission route for coronavirus disease 2019 (COVID-19). There is an urgent need to harmonize discussions about modes of virus transmission across disciplines to ensure the most effective control strategies and provide clear and consistent guidance to the public. To do so, we must clarify the terminology to distinguish between aerosols and droplets using a size threshold of 100 μm, not the historical 5 μm ([ 1 ][1]). This size more effectively separates their ...

The update officially acknowledges growing evidence that under certain conditions, people farther than six feet apart can become infected by tiny droplets and particles that float in the air for minutes and hours, and that they play a role in the pandemic.

"The total airborne mass fraction was between 2.7% and 32.2% of the mass emitted from the bottle, depending on the product. Between 0.0001% and 0.01% of the total airborne mass fraction consisted of residual particles. However, these particles had a mass median aerodynamic diameter between 1.9 µm and 3.7 µm, constituting a total respiratory deposition of up to 77%...Thus, the use of cleaning sprays can result in chemical airway exposure, with particles in the relevant size range for both nasal and alveolar deposition"

HCPs within 1.829 m of patients with influenza could be exposed to infectious doses of influenza virus, primarily in small-particle aerosols. This finding questions the current paradigm of localized droplet transmission during non-aerosol-generating procedures.

The vast majority of studies reviewed here concern hospital and other health facilities where viruses are a well-known cause of occupational and nosocomial infec-tions. Studies on other indoor environments, on the other hand, including homes, non-industrial workplaces and public buildings, are scarce. The lack of regulations, threshold values and standardized detection meth-ods for viruses in indoor environments, make both research and interpretation of results difficult in this field, hampering infection control efforts. Further research will be needed to achieve a better understanding of virus survival in aerosols and on surfaces, and to elucidate the relationship between viruses and indoor environmental characteristics.