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microCOVID / microCOVID

Estimating the COVID risk of ordinary activities
https://www.microCOVID.org
MIT License
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Consider lingering aerosols in calculations #1035

Open blanchardjeremy opened 3 years ago

blanchardjeremy commented 3 years ago

I've heard a few folks ask about aerosols in the last couple months. I think our choice so far has basically been to disregard it as a feature or offer people workarounds as 1-1 advice.

Ran across this and wanted to post it: This article highlights the viral load of aerosols vs coarse droplets. Article: https://www.sciencedaily.com/releases/2021/08/210811131535.htm and original paper https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciab691/6343417

Conclusion of the paper:

Fine aerosols (≤5μm) produced by talking and singing contain more SARS-CoV-2 than coarse aerosols (>5μm) and may play a significant role in SARS-CoV-2 transmission. Thus, exposure to fine aerosols should be mitigated, especially in indoor environments where airborne transmission of SARS-CoV-2 is most likely to occur. While COVID-19 patients early in the course of illness are likely to shed detectable levels of SARS-CoV-2 RNA in respiratory aerosols, culturing SARS-CoV-2 from these patient aerosol samples remains challenging. Person-to-person variation in virus emission is also high. Careful focus is needed on sampling methodology and duration, infectiousness of patients during sampling, and virus culture methodology. Whether isolating viable virus in respiratory aerosols can be more easily accomplished from sampling patients infected with emerging SARS- CoV-2 variants is an urgent enquiry for future investigations. Reducing airborne transmission by altering or averting direct airflow exposure in singing and speech situations indoors may be important practical options to adopt.

beshaya commented 3 years ago

I've heard a few folks ask about aerosols in the last couple months. I think our choice so far has basically been to disregard it as a feature or offer people workarounds as 1-1 advice.

You might be confused, microCOVID is primarily based on aerosol mitigations, we mostly disregard coarse droplets and completely disregard fomites. Outdoors, high efficiency masks, and ventilation only make sense for aerosols transmission.

Or do you mean lingering aerosols, like considering people who were in a room before you?

jy2wong commented 3 years ago

"visited the dentist" comes to mind. As do locations like a gym, where people are not evenly distributed and the room is much larger than the 15 ft radius we ask about in the calculator.

blanchardjeremy commented 3 years ago

Yes I do mean lingering aerosols. Good clarification.

beshaya commented 3 years ago

Has your dentist been using high speed tools during the pandemic? Mine went back to using all manual tools. Could we work this into voice (figure these tools are similar to loud talking or singing?)

I'd be curious for someone to run a gym scenario through Jimenez's aerosol calculator. My understanding is that gyms are usually required to have 4+ air changes per hour, which would tend to clear out aerosols from people far from you. But not everything is up to code.

A thought I had - change the radius based on the environment: plane - how many of the seats immediately around you are full? (plane ventilation is crazy, there was a paper that suggested that aerosols from more than 3 rows away were undetectable) indoors in a home or stuffy space - how many people are in the building with you grocery store or commercial space - how many people are within 15 feet of you (.5-2 ACH, mostly concerned about density) outdoors - 6 ft of you Train - 10 feet (Bart has really good ventilation, not sure what standards are elsewhere)

Also I don't think 10+ feet should give any further reduction if there's no ventilation. Questionable if 6 feet should.

On Wed, Aug 25, 2021 at 4:03 PM Jenny @.***> wrote:

"visited the dentist" comes to mind. As do locations like a gym, where people are not evenly distributed and the room is much larger than the 15 ft radius we ask about in the calculator.

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