PSI
Blog 20210524 Sixty-year paradigm shift in epidemiology exposes the aerosol
screwup
Sixty-year
paradigm shift in epidemiology exposes the aerosol screwup
I know this is a bit
off-topic, but not by much. Remember that right after George Floyd was
murdered, I wrote PSI Blog 20200601 entitled:
“Coronavirus Hates the Outdoors”
From a few news reports, it had seemed obvious to me that
Covid-19 was spread mostly via bad breath, which is only a problem when
ventilation is bad and a room is crowded. Subsequent political demonstrations
and gatherings resulted in very few Covid cases, with less than 0.1% of the
infections from outdoor activity. On the contrary, cases escalated when bars,
restaurants, and churches prematurely opened to crowds eager to test the power
of prayer and jubilation.
Unfortunately, epidemiologists in the USA at first
recommended that we not wear masks and that air purifiers with HEPA filters were
unneeded in crowded rooms. Then they finally recommended we wear masks of any
type, which might be nice for preventing transmission of droplets, but not so
nice for preventing reception. For that, you probably would need N95 masks,
which were in short supply. They work best because, unlike surgical masks, they
can screen out particles as small as 0.3 microns.
Below I have a link to a wonderful article that nicely tells
the story of another nonsensical mainstream paradigm not unlike the Big Bang
Theory I normally rant against. It is worth your time reading. It starts with a
fellow named Wells who studied measles in the ‘40s, finding its transmission to
be aerosolic. He was heavily criticized because the mainstream down-played
aerosol transmission just as it did until recently when Linsey Marr and
colleagues unearthed Wells’ seminal work. The cutoff was thought to be 5
microns, and those would drop out of the air quickly. That is where the 6-ft
trope came from. That, of course, does no good if the air is filled with <5
micron-particles, which settle according to Stokes Law and tend to float around under Brownian motion for hours and hours.
Megan Morteni’s fascinating story is much like the one we
are now faced with in our campaign to get rid of the Big Bang Theory. It is not
quite as absurd as the explosion of the entire universe out of nothing, but it
shows how stubborn otherwise supposedly intelligent folks can be in the face of
clear evidence. Science is supposed to reverse its tune when incontrovertible
evidence shows up—but don’t count on it. Happily, WHO and CDC, after 60+ years
and 16+ months of Covid, has finally and quietly adopted the aerosolic theory.
Bet you didn’t hear any grand announcements in the press. I also bet Einstein
adoration will diminish similarly when relativity and the BBT fade away. Read
now about the mighty, deadly crash of a paradigm that has now met its deserved
end:
“Screwup That Helped Covid
Kill
All pandemic long, scientists brawled over how the virus
spreads. Droplets! No, aerosols! At the heart of the fight was
a teensy error with huge consequences.”
A staider article signed
on by 39 authors, no less, in the mainstream journal Science put the coup de grĂ¢ce on the no aerosol trope:
A paradigm shift to
combat indoor respiratory infection
Building
ventilation systems must get much better
Lastly, remember
this from Healthline:
“Surgical masks do
not provide the wearer with a reliable level of protection from inhaling
smaller airborne particles. N95s filter out at least 95 percent of airborne
particles.
Surgical masks leak
around the edge of the mask when the user inhales. When properly worn, N95s
have minimal leakage.”
In other words, all
masks tend to protect others, but only N95s protect the wearer. KN95s are not
yet approved by NIOSH. Their quality depends on the manufacturer. Unfortunately,
some KN95s really should be labeled N70s.
1 comment:
I live in the Lower Mainland of BC. Based on how rapidly the numbers of cases were increasing by February 2020 I was confident that COVID-19 was spreading through aerosols. So I stopped going into buildings other than my home when BC recorded its 8th case of COVID-19 on February 29, 2020. I find it difficult to believe that there were any competent epidemiologists who were not well aware by January 2020 of the strong likelihood that aerosols were the primary mode of transmissions of this virus.
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