Reducing transmission of SARS-CoV-2 [View all]

[NNadir]

This somewhat scary "perspective" is found in the current issue of Science: Reducing transmission of SARS-CoV-2 (Kimberly A. Prather1, Chia C. Wang2,3, Robert T. Schooley4 Science 26 Jun 2020: Vol. 368, Issue 6498, pp. 1422-1424)

I presume it's open sourced:

Some excerpts:

Respiratory infections occur through the transmission of virus-containing droplets (>5 to 10 µm) and aerosols (≤5 µm) exhaled from infected individuals during breathing, speaking, coughing, and sneezing. Traditional respiratory disease control measures are designed to reduce transmission by droplets produced in the sneezes and coughs of infected individuals. However, a large proportion of the spread of coronavirus disease 2019 (COVID-19) appears to be occurring through airborne transmission of aerosols produced by asymptomatic individuals during breathing and speaking (1—3). Aerosols can accumulate, remain infectious in indoor air for hours, and be easily inhaled deep into the lungs. For society to resume, measures designed to reduce aerosol transmission must be implemented, including universal masking and regular, widespread testing to identify and isolate infected asymptomatic individuals.

Humans produce respiratory droplets ranging from 0.1 to 1000 µm. A competition between droplet size, inertia, gravity, and evaporation determines how far emitted droplets and aerosols will travel in air (4, 5)...

...it is possible that submicron virus-containing aerosols are being transferred deep into the alveolar region of the lungs, where immune responses seem to be temporarily bypassed. SARS-CoV-2 has been shown to replicate three times faster than SARS-CoV-1 and thus can rapidly spread to the pharynx, from which it can be shed before the innate immune response becomes activated and produces symptoms (6). By the time symptoms occur, the patient has transmitted the virus without knowing...

...The U.S. Centers for Disease Control and Prevention (CDC) recommendations for social distancing of 6 feet and hand washing to reduce the spread of SARS-CoV-2 are based on studies of respiratory droplets carried out in the 1930s. These studies showed that large, ∼100 µm droplets produced in coughs and sneezes quickly underwent gravitational settling (1). However, when these studies were conducted, the technology did not exist for detecting submicron aerosols...

...Measurements now show that intense coughs and sneezes that propel larger droplets more than 20 feet can also create thousands of aerosols that can travel even further (1). Increasing evidence for SARS-CoV-2 suggests the 6 feet CDC recommendation is likely not enough under many indoor conditions, where aerosols can remain airborne for hours, accumulate over time, and follow airflows over distances further than 6 feet (5, 10)...

The article goes on to suggest an explanation of why Taiwan, despite having no lockdown, had a low infection rate, while the United States didn't.

Hint: Not that we wish to offend members of the Trump cult here at DU, it involves, um, masks. The article suggests that "social distancing" may not be enough.


A graphic:



The caption:

Masks reduce airborne transmission.

Infectious aerosol particles can be released during breathing and speaking by asymptomatic infected individuals. No masking maximizes exposure, whereas universal masking results in the least exposure.

It is important to note, and it's easy to forget this, that wearing a mask does not protect the wearer so much as it protects other people. This explains the Republican resistance to wearing them. They just don't give a shit about other people.