How would we run experiments to determine the prevalence of aerosol COVID19 spread (long time and long distance) versus droplets?
The droplets vs aerosol debate for COVID19 is heating up. WHO has revised it's aerosol evidence review here: www.who.int/news-room/commentaries/detail/transmission-of-sars-cov-2-implications-for-infection-prevention-precautions Section on airborne transmission.
I'm trying to understand what experiments would need to be run to
determine if aerosol (long time, long distance) is possible.
determine the "prevalance" of aerosol transmission. Here, let's say "<6ft" vs >6ft" infection.
Some snippets:
no studies have found viable virus in air samples.(29-36) Within samples where SARS-CoV-2 RNA was found, the quantity of RNA detected was in extremely low numbers in large volumes of air and one study that found SARS-CoV-2 RNA in air samples reported inability to identify viable virus.
[on superspreading events] However, the detailed investigations of these clusters suggest that droplet and fomite transmission could also explain human-to-human transmission within these clusters.
I'll provide my answer below, but I'll pick the best answer from someone else.
Why I ask
I'm trying to write some online risk tools and calculators. See tinyurl.com/covid3particles search tags: covid19, covid-19, coronavirus, droplet, 5um
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A potential "ideal" experiment is a small, non-ventilated room. A known infected person is in that room for an hour or two. That person leaves and 5 minutes later a susceptible person (or persons) enter and stay in the room for several hours.
(This is not ethical, since it's not okay to knowingly make someone sick. It'd be nice to say CDC says it's mainly droplets and you won't get infected, but this won't pass ethics review.)
You'd also have to isolate that person for the incubation period (5-14 days, for example) to make sure they didn't accidentally get the virus from fomites or large droplets.
And that's the trouble... the ideal treatment+control experiment isn't ethical.
It's also hard to rule out "other explanations" if one uses observational data.
The "observation studies" of HVAC and cruises or Skagit choir have potential confounds (you can't prove they didn't get it from the cookies/snacks).
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With regards to prevalence, I use the Jose Jimenez tool and the Wells-Riley model docs.google.com/spreadsheets/d/16K1OQkLD4BjgBdO8ePj6ytf-RpPMlJ6aXFg3PrIQBbQ/edit#gid=519189277 This gives estimates of the quanta and a numerical probability of infection from aerosol. If there were a numerical probability of from droplet then the prevalance would simply be the ratio of the two.
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