Virus, incubation and contagiousness

My family (well, my brother’s family) has been passing this stomach bug around for the last 3 weeks. SIL’s sister brought it from Washington DC, infected SIL’s parents, then SIL a week after the sister had left, and now my mom (who cares for bro & SIL’s baby at their house) got it this weekend, a week after SIL was done with it.

My dad hasn’t gotten it yet but I think he’ll be next. We’re not sure if bro got it or if he just stressed himself out with caring for a sick wife and infant. I’m the last one standing.

Today my mom asked me to go somewhere with her (the first day she’s been able to eat) and I said no, I didn’t want to be in a car with her for any length of time.

So my question is this…are people passing this bug along before they get the illness, during the illness, or after the illness?

“every virus is different and there’s no way to know” is an acceptable answer. But I’d also like some tips as to when you think it would be acceptable to share air with my mom again.

The norovirus (winter vomiting virus) is extremely transmissible, and can easily be spread by vomit aerosols.

I would avoid anyone who has had the virus for several days post-infection (people can remain infectious for up to 2 weeks), and use all possible hygiene measures for that long.