It is somewhat mystifying that this issue went through any variations. It is, and was, well known that aerosols can infect people at considerable distance from the infected individual, who is venting virion-laden particles into the air (1).
Vocalizing by speaking, yelling and singing are the most efficient means by which small particles form and vent from an infected person. The vocal cords, rapidly vibrating, is an ideal mechanism for generating very fine particles, and send them immediately out into the air. Small particles can drift considerable distances (2), and remain suspended in the air for extended periods. They are quite small, ranging from ca. 1 um to 5 um, and perfect for deep lung penetration.
Quoting from (2):
"Aerosols are generally poly-dispersed droplets and particles which have many different sizes. Classical airborne aerosol hygiene research described droplets of respiratory secretions evaporating to become “droplet nuclei”, which remain suspend in air currents or turbulence and may drift away considerable distances (>1 m) (Keene, 1955). Modern researchers generally use the phrase “droplet nuclei” to refer to respiratory aerosol droplets with aerodynamic diameter <5 μm, and some disease transmission research now refers to respiratory droplets in this size range as “aerosols”. Particles and droplets with aerodynamic diameter <5 μm have the ability to readily penetrate deep into the alveolar region of the lungs of a bystander (Buonanno et al., 2020). In contrast, relatively large droplets are thought to arise from the upper respiratory tract and settle quickly and relatively close to their source."
end quote
There is no doubt this virus can be spread by very fine particles emitted from an infected and shedding individual. To be sure, it is likely to be a very significant source of infectivity. People need to think about how they might minimize aerosol-generated particles in order to minimize viral spreading. Simply lowering voice levels could have a significant advantage in enclosed spaces. Loud voices and singing should be banned when conditions dictate a need for minimal aerosols.
This form of infection - by aerosols - is one of the reasons masks play such a critical role in minimizing viral transmission.
The science tells us that a mask might save your life, or others from you.
"Aerosol emission and superemission during human speech increase with voice loudness"
(1)
https://www.nature.com/articles/s41598-019-38808-z
"Aerosol transmission of SARS-CoV-2? Evidence, prevention and control"
(2)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7413047/
Facebook
Twitter
Instagram