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Dr. Shelly Miller, PhD Profile picture
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13 Sep, 6 tweets, 1 min read
Check out our great new paper led by Dr. Wagner: Modeling the impacts of physical distancing and other exposure determinants on aerosol transmission. Glad to be a part of this analysis, with amazing colleagues Drs. Sparks, Chen, Waldman and Dr. Macher oeh.tandfonline.com/doi/full/10.10…
a particle size-dependent aerosol release model was developed to assess impact of near-field transport of infectious aerosol. This is essentially what is happening when you are standing close to someone that is infectious...
we find that short-range (proximity) and long-range (background) transmission is additive and so both must be mitigated at the same time.
increasing ventilation is critical but it's impact is not great as suspected when you are closer to an infectious person (near-field). Distance, emission rate, and exposure duration are also important. but air direction and inhalation rate are not that important.
Surgical mask and respirators were 10-100 times more effective at reducing risk than cloth masks.
and...outdoors the risk is really low ...

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More from @ShellyMBoulder

Dr. Shelly Miller, PhD Profile picture
14 Apr
Measurements and Simulations of Aerosol Released while Singing and Playing Wind Instruments.The preprint of our paper is now available! scholar.colorado.edu/concern/articl… Our amazing research team includes @marinavance @mspede @Don_Milton @James_Weaver_83
ABSTRACT: Outbreaks from choir performances, such as the Skagit Valley Choir, showed that singing brings potential risk of COVID-19 infection. There is less known about the risks of airborne infection from other musical performance,
such as playing wind instruments or performing theatre. In addition, it is important to understand methods that can be used to reduce infection risk. In this study, we used a variety of methods,
Read 8 tweets
Dr. Shelly Miller, PhD Profile picture
8 Jan
1/ ICYMI paper on variant linking epic and genetic data: imperial.ac.uk/media/imperial… 1. the variant does appear to be more transmissible. From my read of the paper, it accounts for about a half to 2/3 of an additional infection per every additional transmission.
2/ SO for example if I have COVID and I give it to my husband, highly likely, then if I had this variant, I might also give it to 1/2-2/3 of another person - which is not physically possible, of course!
3/ I might also give it to my son resulting in 2 infections, but then the next person with the variant may only give it to one additional person, so between the 2 of us with the variant, the result is 3 additional infections instead of 2 if we were transmitting the non variant.
Read 8 tweets
Dr. Shelly Miller, PhD Profile picture
10 Dec 20
1/My public comments to the @BVSDcolorado board meeting on 12/8. I am an engineering professor @CUBoulder and an expert in engineering controls for airborne infectious diseases. @DougChem @epibuff
2/I was instrumental in helping CU Boulder open its campus safety. we have had ~50 cases of COVID-19 positive students in the classrooms and not a single case of transmission.
3/This pandemic is uniquely defined by superspreading events. These account for a majority of the cases but are caused by <20% of the infectious. This is through long-range exposure and mitigated by reduced occupancy indoors and improved ventilation and air cleaning.
Read 15 tweets
Dr. Shelly Miller, PhD Profile picture
2 Nov 20
1/13 MOST HOMES ARE POORLY VENTILATED. WHAT DOES THIS MEAN FOR COVID-19? Most homes in the US are are poorly ventilated. There is no mechanical system supplying outside air indoors and exhausting indoor air outside. Read the entire post here: shellym80304.com/2020/11/02/mos…
The way homes are typically ventilated is by opening a window and/door, or by air leaking in (or infiltrating) through unintentional openings and cracks in the building shell. Homes recirculate indoor air through coarse filters when the heating or cooling system is operated.
Why is this important? Because the risk of infection with SARS-CoV-2 increases substantially when you are sharing the air in a poorly ventilated space with an infected person. The majority of transmissions happen within the household.
Read 13 tweets
Dr. Shelly Miller, PhD Profile picture
15 Oct 20
1/5 The bottom line is that on school openings many districts are still operating as if it were Mar not Oct. In Mar most of us did not know how the virus was transmitted (too bad WHO did not tell us in Feb). Now we know & we know what do to do minimize airborne transmission
2/5 The goal is not to suppress every single case, but construct our indoor environments to minimize the potential for large spreading events. Schools can be safe low-risk spaces if they are following our (@linseymarr @j_g_allen @jljcolorado @CorsIAQ) recommended protocols.
3/5 That doesn’t mean that cases are not going to occur and be brought to school. What we don't want is spreading wishing school. We’re trying to support the idea that we need to live with this virus. There is not enough political leadership or will to do otherwise in the US.
Read 6 tweets
Dr. Shelly Miller, PhD Profile picture
1 Oct 20
1/4 Just so you know: my entire motivation for talking about how COVID is transmitted is to keep people safe. If it was clearly transmitted via fomites, then I would be talking about washing your groceries. And that is what I would be doing (I am not)
2/4 If it was only transmitted by large spray droplets then I would focus on supporting efforts to get acrylic partitions and shields on everyone. (and I would have a shield but I don't, I do wear glasses/googles with my mask)
3/4 I am not happy that this thing is airborne, that you can inhale randomly floating viruses when you spend time indoors from some asymptomatic person w/o following suggested guidelines for reducing risk. I follow the science. (I don't share the air with others)
Read 4 tweets

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