COVID19 transmission - Printable Version
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COVID19 transmission - BostonCard - 05-11-2020
This was a really good blog post about risk of COVID-19 transmission over various settings.
https://www.erinbromage.com/post/the-risks-know-them-avoid-them?campaign_id=9&emc=edit_nn_20200511&instance_id=18384&nl=the-morning®i_id=112348342&segment_id=27239&te=1&user_id=ceb8dc75e6018f57e5d7fc74f24220a2
The full blog post is worth reading. It goes over the principles of transmission (including the idea of "infectious dose", which is really an ID50, or the dose that will cause infection in 50% of people exposed), which is basically a factor of the product of time and exposure intensity. It also talks about why the risk is much higher indoors than outdoors, and why the risk is much higher in a small closed environment: "All these infection events were indoors, with people closely-spaced, with lots of talking, singing, or yelling".
I found this advice to be helpful:
Quote:Basically, as the work closures are loosened, and we start to venture out more, possibly even resuming in-office activities, you need to look at your environment and make judgments. How many people are here, how much airflow is there around me, and how long will I be in this environment. If you are in an open floorplan office, you really need to critically assess the risk (volume, people, and airflow). If you are in a job that requires face-to-face talking or even worse, yelling, you need to assess the risk.
If you are sitting in a well ventilated space, with few people, the risk is low.
BC
RE: COVID19 transmission - M T - 05-11-2020
Don't stop with that blog. Follow the link to the article that inspired it.
https://quillette.com/2020/04/23/covid-19-superspreader-events-in-28-countries-critical-patterns-and-lessons/
The author has collected 54 super-spreader events, and presents common characteristics. I appreciated that he thought about what wasn't in his collection. His opinion is that these suggest that spread is by large droplets, at least for these events.
IMO, I think these events mostly have the same characteristic of being easily characterized. It is like looking at the danger of guns by looking only at mass shootings. As someone else here said, how are you going to know that you got infected by a nameless jogger that passed you on the street, you'll blame something else that fits an expected model. Other avenues such as movie theater or class attendance, he classes as quiet observation with few large droplets emitted. But I'd say the world has had few of those since the disease has spread, so it is early to dismiss those.
I don't think he mentioned the Huanan Seafood Wholesale Market in Wuhan. It appears to be a combination of interior & exterior (where items are sold), but the exterior is crowded & noisy. I can imagine there are cold areas in the market, not shown in the video.
A pair of interesting videos, from the same Indian tourist source: Wuhan 2020 (before COVID). A long tour of a seafood wet market is shown beginning at 1:20, but I can't confirm it is the infamous market where the disease spread early. And a post-lockdown Wuhan 2020, featuring mostly a Walmart-like food store.