

Since folks are likely considering quarantining before gathering this season @Ymax, @JustinLessler & I put together a quick explainer on why 14 days is recommended

Where does 14 days come from?
Scientists have been collecting data on the number of days from when someone is infected until they show symptoms. They can then plot this data and look at the shape to gain an understanding of the incubation period.

There have been lots of studies that do this, and all of them show a pretty similar shape, with a peak at 4–7 days and a tail that extends out at least 2 weeks. Combining all of the data from all of these studies gives an even better estimate.
Let's look at the cumulative distribution. If we add up everyone with symptoms by day 10 & divide by the total number of people, we see that 91% show symptoms by day 10. Doing this across all days helps us know what percent of infected folks will see symptoms by a certain time.
What about a 10 day quarantine? A 10 day quarantine is better than not quarantining at all (and also better than a 9 day quarantine!) but based on what we know about the incubation period, about 9% of infected folks won’t see symptoms until >10 days after getting infected
A 7 day quarantine + negative test is better than not quarantining at all (& better than a 7 day quarantine without a test) but even our best tests have a hard time detecting whether you are sick before you show symptoms & over 25% won’t see symptoms until >7 days post infection
The main take-aways:
If you plan on gathering with folks outside your household, a 14 day quarantine starts today. This means, if you are infected now and going to get sick, you have a 98% chance of seeing symptoms before Christmas, allowing you to cancel your plans



