14 November, Saturday, Day 222

 A lot to blog about today, but I chose Tegnell and the spread of the disease. 

Tegnell and the Spread of the Disease

Tegnell did on November 12 claim that the disease does not spread by air, and that drops is the rule. In special situations, an infected person can create an aerosol which can spread longer. (Lisa Andersson, Omni, torsdagen den 12 november, 21:38)

This is of course complicated, and way outside of my competence. It does, however, seem like the distinction between airborne, aerosol and drops is not that distinct. It also seems like a lot can go wrong if incorrect assumtions are made.

The quote below, under "Swedish", could be wrong or it could be dated, it did, however, make me think. 

SWEDISH

Mycket att blogga om idag, men valet föll på Tegnell och smittspridningen. 

Tegnell och smittspridning

Tegnell menade den 12 november att smittan i huvudsak inte är luftburen, men att regeln är att det rör sig om droppsmitta. I speciella situationer kan en smittad skapa en aerosol som kan spridas något längre." (Lisa Andersson, Omni, torsdagen den 12 november, 21:38)

Det här är naturligtvis knepigt, och utanför min kärnkompetens. Det verkar dock som att gränserna mellan luftburen, aerosol och droppsmitta inte är absoluta. Det verkar också som att mycket kan gå fel om man gör fel antaganden från början. 

Nedanstående citat kan vara föråldrat eller fel, men det gör mig fundersam. 

Kimberly A. Prather, Chia C. Wang, Robert T. Schooley

Science 26 Jun 2020

"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. As a comparison, calculations predict that in still air, a 100-µm droplet will settle to the ground from 8 feet in 4.6 s, whereas a 1-µm aerosol particle will take 12.4 hours (4). 

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)."

https://science.sciencemag.org/content/early/2020/06/02/science.abc6197.1