Earlier quoted context omitted.
Have you got a link for the 24 days? The best I could find is that we're totally guessing things at this point. CDC says: > CDC believes at this time that symptoms of 2019-nCoV may appear in as few as 2 days or as long as 14 after exposure. This is based on what has been seen previously as the incubation period of MERS viruses.
The 24 days reference is from this paper https://www.medrxiv.org/content/10.1101/2020.02.06.20020974v...
> The median incubation period was 3.0 days (range, 0 to 24.0 days)