Big thank you to @EricCarroll for pointing out this new WHO document on SARS-CoV-2 transmission.
This document is pretty complex, in-depth, dense, and I still expect it to evolve as we learn along the way. They have some of the correct people to be working on this, for once. Hello Lidia Morawska signing off on it at the beginning of the forward.
First, a tldr. If you don't care about how it came to be, or the science, and just want to know the outcome, here it is:
https://partnersplatform.who.int/tools/aria
Go to the calculator, enter your data, and come out with a probability of infection in a given situation along with the number of expected secondary infections from that interaction.
Here's the document itself if you want to follow along:
https://iris.who.int/bitstream/handle/10665/376346/9789240090576-eng.pdf?sequence=1&isAllowed=y
Disclaimer - This is evolving science.
I'm going to split this up in a thread, because I took a lot of notes of what stood out to me on a first read, and I hope to come back to it, and use it as a general reference moving forward.
Next is what they're calling the viable virus factor. I think we've all wondered how long is SARS-CoV-2 viable and in what scenarios, and there's a lot of variables, honestly. Here's what they based their model off of:
"Viable virus factor
Viable SARS-CoV-2 was identified in air samples from rooms occupied by COVID-19 patients in the absence of aerosol-generating health-care procedures [116] and in air samples from an infected person’s car [117].
...
While in laboratory experiments, SARS-CoV-2 stayed infectious in the air for up to 3 hours with a half-life of 1·1 hour [119], a systematic review looking at the range of ratio of viral copies in aerosol to plaque forming units (PFU) ratio returned values in between 6 to 0.343 log10 viral copies/litre of air and in between 2.15E+03 to 2.68E+04 TCID50/100 μm for viral titre [116], [120] and RNA to PFU [116] respectively."
I've certainly read numbers longer than 3 hours before, but don't have a reference handy. This might be one variable that I take issue with, but I'm not sure off hand.
@BE Dr Eric Feigal Ding (epidemiologist) posted solid evidence that Covid stays in the air for up to 16 hours.
I'm right there with you from my memory. In annex 1, Q3, they provide 8 studies and a half life of 1.1 hours came up twice, once in a model and once in an experimental, and were each the largest values there. I'd have to dig further into this one to have a fully formed scientific opinion.
This one's been bugging me all day! So, that paper does exist that we both remember:
https://www.medrxiv.org/content/10.1101/2020.04.13.20063784v1
There's nothing after it, that I found in a quick search, that came anywhere close to 16 hours. I'm considering it an outlier at this point.
I am very much a Professor Jimenez fan(@jljcolorado please come back to Mastodon!) and his paper said that aerosols from speaking can linger for 9 hours.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8349476/
I think a large part of it is the variability across different atmospheric conditions:
https://www.pnas.org/doi/full/10.1073/pnas.2200109119
Perhaps the answer is really just "hours"
