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 up, masking yourself when not sick. I don't want to get too deep into the weeds on this. It's good that we're discussing the efficacy of masking and that it's recommended, AND that they discussed fit as being important. I've long wondered if we're ever going to get to a place where people not only mask, but care about the fit. Probably not on a large scale, but, this is about protecting yourself at this point. Masks work.
"Masks and Respirators (Inward)
The use of face coverings has been promoted as a
key measure to reduce the SARS-CoV-2 transmission throughout the pandemic. Specific types of face coverings including but not limited to respirators, surgical masks and cloth masks have been recommended for healthcare facilities [121], [122] and community settings [123] according to the level of risk and protection required. In the absence of mask mandates, the compliance of face coverings is an important parameter, hence the exact quantification of the risk reduction provided by the use of face coverings is highly dependent on the level of compliance. In addition, the mask composition and fit [124], [125] are also of high importance, where the standard requirements for filtration efficiency and fit are defined by NIOSH-42 CFR Part 84 [126], EN 149 [127] and ASATM F3502-21 [128]. In order to estimate the overall transmission risk, filtration efficiency values for this model have been extracted from experimental studies (Annex 1) that measured the inward and outward filtration efficiency of different types of masks for a given size of particles, with information on particles ranges, respiratory activity, particle velocity and airflow. Ultimately, however, the fit effect on the wearer’s face is probably the most significant parameter."
