Any specialists in viruses here?
Yes (me)
I always thought that sick bugs were not airborne.
Strictly speaking not airborne, not like measles, but there's always Projectile vomit, resulting in aerosols, lovely (not !)
Don't rule out residue left on surfaces, your sofa even. Noro is very hardy, it can persist on surfaces for days and days. With low residual resistance, we all probably need just a little dose to become ill with it.
big event at the weekend and my parents had been poorly ...Now all but one of us are throwing up/diarrhoea.
Don't worry, the "but one" will have a turn...
timing matters, Noro has incubation period with median = about 33 hours. Today is Tuesday evening. If gap from you last saw your folks to when any symptoms in your household started was > 48 hours, that suggests not direct transmission but rather via surfaces.
The other possibility is that you got it from somewhere/someone else.
Other people in the world have tum bugs. Tots/Little kids shed noro for days & days after they seem fully recovered. We do get medium-term immunity to it afterwards, so that's nice. And it's usually finished in 36 hours.
A common feature of Noro is that it comes on fast, you go from feeling fine to feeling awful (spewing) in 20-60 minutes. Is that how you guys became ill?
Many other Germs are available, they could be your lurgy instead.