What's the upper bound of how long COVID is contagious?

post by Raemon · 2020-03-21T22:39:30.829Z · score: 13 (3 votes) · LW · GW · 3 comments

This is a question post.

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  Answers
    5 lexande
    1 waveman
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3 comments

A key question for people figuring out good longterm isolation practices is "how long do I have to be symptom-free before I'm 'certified safe'?"

This post on the typical-course-of-COVID-19 [LW · GW] provides some studies that inform on the question, but doesn't directly answer it yet.

I recall hearing something like "most cases last less than two weeks", but I'm not sure if two weeks is actually a strong enough upper bound that I'd feel comfortable encouraging lots of people to act on it.

This contains two subquestions:

(I'm personally most interested in the answer to the second question right now, but both seem important)

Answers

answer by lexande · 2020-03-22T06:43:02.475Z · score: 5 (4 votes) · LW(p) · GW(p)

Since apparently some confirmed cases never develop symptoms (this study of Diamond Princess passengers estimates 18%), it seems the answer to your second question is "never"?

comment by Raemon · 2020-03-22T07:53:48.599Z · score: 2 (1 votes) · LW(p) · GW(p)

Sorry, I worded that wrong. Edited the OP.

answer by waveman · 2020-03-22T22:58:37.082Z · score: 1 (1 votes) · LW(p) · GW(p)

Worth pointing out that if we quarantine for X days and do not actually test, relying on symptoms, then we are selecting for slow incubation and/or mild/no symptoms before X days.

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comment by Scott Garrabrant · 2020-03-22T03:26:34.201Z · score: 5 (3 votes) · LW(p) · GW(p)

You should (more strongly?) disambiguate between how long after being sick are you safe, or how long after being 100% isolated are you safe.

comment by Raemon · 2020-03-22T03:42:13.576Z · score: 2 (1 votes) · LW(p) · GW(p)

Updated OP to explicitly flag that there are two sub-questions here. (I assume both will benefit from similar aggregated information)

comment by Sjcs · 2020-03-22T06:34:15.697Z · score: 1 (1 votes) · LW(p) · GW(p)

TL;DR We don't know, it's variable case to case, and could be longer than 25 days from symptom onset if you get sick

In patients admitted to hospital with COVID-19, there are cases (Korea, Singapore) of viral RNA detectable up to 25 days after symptom onset. This is not the same as still being infective, so we don't really know.

In people exposed to SARS-CoV-2, 14 days is an estimation that the vast majority will have developed symptoms by this time (here). However, this doesn't take into account cases that remain asymptomatic throughout their infection (maybe 15-20% from Diamond Princess data)