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Dr. Alex Huffman Profile picture
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3 Feb, 6 tweets, 4 min read
Updated preprint on COVID risk modeled from respiratory aerosol data

Notice ⬇️:
- No "safe" distance indoors, b/c aerosols travel
- Masks & ventilation increase safe time, but still risk

Graphs: below each line = safer

HT @linseymarr & @kprather88 (1/x)
medrxiv.org/content/10.110…
2/ Study used the #WellsRiley model to estimate COVID risk from respiratory aerosols in a variety of scenarios, using particle size distribution data from previous studies.

Quanta: Statistical measure of avg infection probability; bigger value = easier to infect [~1 - e^-quanta]
3/ Bazant & Bush study supports broad consensus of observation & preventative steps:

✅No single action sufficient for COVID prevention
✅Steps compound reduction in risk, but never to zero
✅All important: distance, masks, reduced time, incr. ventilation
medrxiv.org/content/10.110…
4/ To be clear - Observations in the paper above are very useful, but the method also looks only at room-mixed aerosol. Risk of airborne infection is likely still highest from aerosol nearest the emitter, adds to above = why distance & masks are critical.
5/ Also, this study is good & based on a simple model that has been widely applied. Uses assumptions informed by previous observations to calc. risk. Observations also not really new, but broadly consistent w/ recommendations.

To calc for yourself:
6/ There is still a lot of confusion about aspects of adequate prevention strategy wrt COVID. If you want to dig a bit deeper, this is an easy-read article debunking common myths of airborne virus transmission & supporting reasons for the preventions above.journalofhospitalinfection.com/article/S0195-…

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More from @HuffmanLabDU

Dr. Alex Huffman Profile picture
1 Feb
Imp. perspective to remember.

"Excessive attention on making surfaces pristine takes up limited time & resources that would be better spent on ventilation or the decontamination of the air that people breathe": @linseymarr

By @dyanilewis HT @rye_b (1/x)
nature.com/articles/d4158…
2/ A few other key quotes/reminders:
“It’s become clear that transmission by inhalation of aerosols — the microscopic droplets — is an important if not dominant mode of transmission,” says Prof. @linseymarr , who studies airborne disease transmission.
3/
 “You have to make up some really convoluted scenarios in order to explain superspreading events w/ contam. surfaces”
“If we’ve already paid attention to the air & we have some extra time resources, then yes, wiping down those high-touch surfaces could be helpful”: @linseymarr
Read 5 tweets
Dr. Alex Huffman Profile picture
30 Jan
Study showing nosocomial (in hospital) transmission of COVID to HCWs despite surgical masks & distancing.

Important b/c:
1) Virus aerosolized w/o AGPs; only possible if airborne
2) Surgical masks insufficient (weak filtration; bad leakage)
via @CPita3 1/x
academic.oup.com/ofid/advance-a…
2/ Conclusions of the study are anecdotal, but they are important b/c they add further direct support to a mountain of diverse evidence suggesting #COVIDisAirborne, though not treated so by #WHO and others.

RT original from @CPita3:
3/ One key, practical take-away: upgrade your #mask quality (#N95, when possible) and always make sure it fits snugly all around to reduce air/virus leakage & transmission risk.
Read 6 tweets
Dr. Alex Huffman Profile picture
28 Jan
My heart is heavy today at the loss of Prof. Paul Crutzen, Nobel Laureate and a giant of both science & humanity, truly with no equal.

So many profound contributions: ozone layer chemistry, nuclear winter, #Anthropocene, +

A few quotes & obs. below (1/x)
mpic.de/4677594/trauer…
2/ "He was the first to show how human activities damage the ozone layer. This knowledge ... was the basis for the worldwide ban on ozone-depleting substances – a hitherto unique example of how Nobel Prize-winning basic research can directly lead to a global political decision.”
3/ “Paul Crutzen was also a pioneer of the sciences focusing on the impact of human civilization on the environment, whether through his findings on the destruction of the ozone layer or through his later scientific work on human-made climate change."
nobelprize.org/prizes/chemist…
Read 9 tweets
Dr. Alex Huffman Profile picture
27 Jan
1/ An interesting editorial by Prof. MacIntyre, infectious disease professor at the @KirbyInstitute at @UNSW. Edited by @mariemcinerney.

She postulates on why the COVID pandemic response has been such a "catastrophic failure of many Western democracies".
croakey.org/the-hijacking-…
2/ For reference, Prof. MacIntyre wrote this scientific editorial with @rajah_mich on 'Scientific evidence supports aerosol transmission of SARS-CoV-2"
aricjournal.biomedcentral.com/articles/10.11…
3/ Much focus on importance of a #multidisciplinary approach. A few interesting quotes:

"The evidence is clear that SARS-COV-2 is airborne, yet guidelines in many countries do not yet reflect this, thus hampering the ability to control the spread and endangering health workers."
Read 6 tweets
Dr. Alex Huffman Profile picture
26 Jan
1/ A really good, short read on a very important topic, providing motivation and support for mandated, high-quality #mask-wearing.

By @sri_srikrishna @MonicaGandhi9 @Don_Milton & others = These people you should trust.
hbr.org/2021/01/a-3-st…
2/ COVID19 still very serious & "widespread vaccination is expected to take multiple years globally."

Key arguments from the article above ⬆️ concerning masks.

1. Launch an awareness blitz
2. Communicate about appropriate mask types
3. Prioritize distribution to the vulnerable.
3/ A really important, practical message to emphasize:

Disposable N95s had been in short supply & "have been largely reserved for health care workers. But N95s are now available [widely]."

Should help motivate use of N95s, which have high & standardized filtration efficiency.
Read 5 tweets
Dr. Alex Huffman Profile picture
25 Jan
1/2 @DrLaPook on the importance of quality face coverings (i.e. N95s or even multiple mask layers), esp. as worrying COVID variants rise (via @linseymarr).

But wrt to multiple #mask layers; mask FIT and overall BREATHABILITY also critical, because ...
cbs.com/shows/cbs_even…
2/2 ... If it's hard to breath through a #mask, it is too restrictive/thick. Air (& aerosol) will always escape mask. If air exits via gaps rather than THROUGH layer(s), mask is ineffective!

E.g. watch where/how aerosol escapes this poorly-fitting mask
3/2 (bonus) Since mask fit is so so important (even for N95s), there are various strategies to help improve air flow *through* the mask layers & improve fit. This preprint paper shows improvement in mask filtration efficiency by adding a mask brace/fitter.
Read 4 tweets

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