On Worldometer, they are still showing a few different median times from being infected to the first symptoms. We’re all accustomed to hearing about the potential 14 days in the media, and for good reason. But it can also be as low as 2 days, apparently. This being such a wide range already, I would think that we should have a much better handle on the mean, as well as the confidence interval, by now. Is this updated anywhere?
Also, is it known which percentage of people know exactly when they became infected? If I became symptomatic today, I would have no way of knowing whether it was from 2 weeks ago, or this past Thursday. But I live in a densely populated area, and it is impossible to completely protect myself, despite following the recommended best practices.
Sometimes the time from exposure to symptoms can depend on how you are exposed.
For example, if you inhale particles in the air, and are infected by absorbing them through your lungs, the incubation period may be* n*, while if you shake the hand of an infected person who ate a sandwich and didn’t wash his hands, and then you rubbed your eyes because they itched, so you transferred the virus through your mucous membranes around your eyes, the incubation may be n + x, or n - x.
I can’t think of any examples off the top of my head, because IANAD, but I have been told by doctors of viruses or bacteria that operate this way.
It may be that researchers are aware of Covid-19 behaving this way, but have not pinned down what all the various rates of incubation are for different types of transfer. So the best they can do is give a range.
IIRC the 14 days number is a calculation rather than based on empirical evidence. The median time for onset of symptoms is apparently 5 days.. 14 days is what the have calculated is the latest time since exposure that symptoms could appear.
Another recent confirmation of 5 days: https://www.sciencedaily.com/releases/2020/03/200317175438.htm.
97.5% will have symptoms before the 12th day.
Seems to me that this is clearly the biggest differentiating factor versus other infections. Social distancing should hopefully help.