If I interact with someone with nCov for an hour, how likely am I to get nCov?
post by Raemon · 2020-03-01T23:53:19.649Z · LW · GW · 1 commentThis is a question post.
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Answers 23 romeostevensit 3 arikr 1 avicennah None 1 comment
I'm guessing data is limited here, but a related-related question might be "how likely am I to catch the flu or a few other common diseases by interacting with a victim for an hour?"
Answers
" In Sichuan province, 25,493 contact persons were named, 25,347 (99%) were found, 23,178 have already been examined and 0.9% of them were infected. In the province of Guangdong, 9,939 contacts were named, all found, 7,765 are already examined and 4.8% of them were infected. That means: If you have direct personal contact with an infected person, the probability of infection is between 1% and 5%. "
↑ comment by Decius · 2020-03-08T01:33:24.134Z · LW(p) · GW(p)
That's not particularly useful without the base rate of infection in those provinces, and it appears to at least double count (assuming 'close contact' is a reciprocal relationship, every case of two people in close contact both being infected would count as two cases of a close contact being infected).
Based on the upper estimate of 2.5 for R_0, those numbers suggest that the average person has fewer than 50 'close contacts', and likely even fewer.
This medium post provides a pretty good answer for this question: https://medium.com/swlh/so-youre-going-outside-a-physics-based-coronavirus-infection-risk-estimator-for-leaving-the-house-d7dcae2746c0
And see also the related calculator: https://sygo.mardillu.com/
Answer depends on several things
1. Where you met, temperature, humidity, degree of ventilation
2. Distance and intensity of interaction and exchange of fomites
3. Degree of infectivity (were they coughing and their viral shedding; where they are in illness course)
4. Hygiene, theirs and yours, including hygienic behaviors
5. Your level of immunity (are you already immune, are you immunocompromised, etc)
↑ comment by Raemon · 2020-05-05T16:31:29.196Z · LW(p) · GW(p)
Do you have a sense on how it depends on any of those things?
Replies from: avicennah↑ comment by avicennah · 2020-05-06T10:34:47.228Z · LW(p) · GW(p)
Transmission risk 1. Goes up with humidity and down with more ventilation and warmer temperatures 2. Higher with smaller distances and fomites
Infectivity 3. Increases with greater viral inoculate (which goes up with more shedding), which is also greater with 4. reduced hygiene and direct contact with mucous membranes. Even at smaller inoculates, 5. an immune incompetent host has higher chances of infection. Happy to provide citations for anything you’re specifically curious about.
Replies from: Raemon↑ comment by Raemon · 2020-05-07T19:58:53.942Z · LW(p) · GW(p)
Thanks. The thing I'm ultimately looking for though is more like "at humidity X, your likelihood is Y". I know roughly how the variables fit together, but not enough to decide "do I let a random person who might have covid into my house or not?"
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