1/ Here is official @CDCgov @CDCMMWR report out today

They assessed various modifications incl:

•wearing a cloth mask over a medical procedure mask (double masking)

•knotting the ear loops of a medical procedure mask & tucking in the sides

2/ Simulation set in a 10x10 foot chamber; aerosols generated simulating someone doing “light work” load and the receiving dummy doing “moderate work”

Pic below of some key mods as described:
3/ “Ten mask combinations, using various configurations of no mask, double masks, and unknotted or knotted and tucked medical procedure masks, were assessed”
4/ “unknotted medical procedure mask alone blocked 42.0% of the particles from a simulated cough (standard deviation [SD] = 6.70), and the cloth mask alone blocked 44.3% (SD = 14.0)”

This should no longer be the standard by which the general public is masked. #BetterMasks
5/ “The combination of the cloth mask covering the medical procedure mask (double mask) blocked 92.5% of the cough particles (SD = 1.9).”

Significant improvement; thought to be due to improved fit provided by the cloth mask. Keep in mind this may not always be true.
6/ “adding a cloth mask over the source headform’s medical procedure mask or knotting and tucking the medical procedure mask reduced the cumulative exposure of the unmasked receiver by 82.2% (SD = 0.16) and 62.9% (SD = 0.08)”

Source control- large range of variability
7/ “When the source was unmasked and the receiver was fitted with the double mask or the knotted and tucked medical procedure mask, the receiver’s cumulative exposure was reduced by 83.0% (SD = 0.15) and 64.5% (SD = 0.03), respectively”

Personal protection - also large range
8/ “When the source and receiver were both fitted with double masks or knotted and tucked masks, the cumulative exposure of the receiver was reduced 96.4% (SD = 0.02) and 95.9% (SD = 0.02), respectively”

When both parties efficient masking, you get very high levels of protection
9/ warning: “double masking might impede breathing or obstruct peripheral vision for some wearers, and knotting and tucking can change the shape of the mask such that it no longer covers fully both the nose and the mouth of persons with larger faces”
10/ Overall important work
“these experiments were conducted with one type of medical procedure mask & one type of cloth mask among the many choices that are commercially available & were intended to provide data about their relative performance in a controlled setting”
11/ “The findings of these simulations should neither be generalized to the effectiveness of all medical procedure masks or cloths masks nor interpreted as being representative of the effectiveness of these masks when worn in real-world settings.” #covid19

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More from @AbraarKaran

10 Feb
Short Thread
1/ Another must-read piece from Dr. Mike Klompas @BrighamWomens - lead author of the recent #covid19 outbreak study from our hospital in @AnnalsofIM- I've been lucky to call Mike a mentor this year & have learned a lot from him
What is an AGP?
2/ "It has become clear that the traditional dichotomy b/w droplet vs aerosol-based transmission is overly simplistic. In practice, people routinely produce a profusion of respiratory particles in a range of sizes that incl both droplets & aerosols as well as particles in b/w"
3/ "Respiratory particles of all sizes can carry virus and all are potentially capable of transmitting infection. The amount of respiratory particles one emits varies by activity. Quiet breathing generates a small but steady flow of aerosols." #covid19
Read 9 tweets
9 Feb
1/ The major #covid19 outbreak from @BrighamWomens where I work is now published in @AnnalsofIM — definitely worth a read. Phenomenally detailed work here from many smart people.

The index patient tested negative twice, but soon became positive after.
2/ “The virus was likely introduced into the facility by a symptomatic patient who tested negative twice on admission but in retrospect was contagious from at least hospital day 3 and infected staff and patients for at least a week before detection” #covid19
3/ The infection control team & overall program at our hospital is awesome. They are among the smartest people I know. And despite all of the protective measures in place, transmission & a serious #covid19 cluster still happened.
Read 19 tweets
8 Feb
"And there’s another problem: too much filtration becomes unbreathable. “Are you breathing through the material, or are you breathing through the gaps in the material?” Zangmeister says.
2/ "If you’re breathing through the gaps in between the mask and your face, you’re not getting any filtration production at all."

#covid19 #BetterMasks
3/ "In lab settings, Zangmeister and his team have found these areas where air escapes tend to be behind the cheeks, or right above the bridge of the nose, which can look like a droplet exhalation geyser, he says. "
Read 5 tweets
8 Feb
1/ One of the issues w/ public health policy making is the lack of accountability or even full understanding of the effects of those policies. Yesterday was an example of this when #LACounty @lapublichealth @MayorOfLA restricted outdoor TVs from playing the #SuperBowl.
2/ I personally know of multiple unvaccinated friends who decided to gather indoors as a result.

It was 70 degrees & sunny in Los Angeles yesterday.

The state already opened outdoor dining & made people feel like it was 'safe' to do this.

But then- they ban TVs outside.
3/ What they are essentially telling the public is that they aren't responsible enough to do this.

That the government decides how responsible you are, rather than mitigating risk & giving you ways to socialize more safely.

And then they wonder why...
Read 11 tweets
7 Feb
The messaging from #LACounty is ridiculous. On the one hand, they opened up all of these restaurants for outdoor dining & made people feel like things are getting better- but they aren’t allowing outdoor TVs to play the Super Bowl? People are going to meet indoors instead...
2/ This is bad public health. It’s just like when beaches were closed during July 4th. We need to mitigate risk & create safe options for socialization - bc people have shown time & time again that they will socialize either way (not blaming them)
3/ Alternatively they could have set up outdoor viewing sites at parks etc; created distanced pods— many ways to get creative here as was done in other places. But just assuming that people won’t congregate when they have been told it’s getting much safer now...?? #covid19
Read 7 tweets
3 Feb
1/ This story saying that a local health dept has changed their exposure time to any contact without masks ("1 second") doesn't mean that you will get infected in one second- but it does point out that 6 feet/15 min is not a hard/fast rule & never was.

2/ There are many possibilities for why new variants are "more transmissible"; but in the real world, figuring out the "why" takes time- and we don't have time. We must utilize the best protections we can right now- mitigation of risk is name of the game

3/ With vaccinations, it seems like our attention to other protection measures have fallen to the side- understandably bc there are only so many resources that public health departments have. Doing one often means not doing another (staff, funding etc)
Read 5 tweets

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