So last Friday night, we had a ‘second’ Thanksgiving dinner at my sister-in-law’s house and I get seated next to a family friend who clearly should NOT have been there. With his wild sneezing, coughing, snotty-nose blowing, etc., it was clear he had the flu…and lucky me…the next night I started to get the same symptoms.
As I sat their cursing the family friend for showing up and giving me his disease, my wife corrected me and swore that the incubation of a cold was a minimum 48hours and that I must have caught the cold BEFORE I ever got to the house. I say that’s bullshit and that this guy gave it to me (i.e. a minimum incubation time of 24 hours).
The answer to your question seems to be, “It depends–we’re scientists and we don’t have to give you a straight answer, and you can’t make us, so nyah nyah nyah.”
I use three days as a general rule & it works very well for me. That’s for a cold, which is mostly a contact virus. Don’t get it confused with the flu, which is airborne.
