My Mum had this at the beginning of the week, luckily it is a short-term illness. I also know a couple of friends who were contracted and it really isn't a nice thing to have. It's weird that no-one else in our family caught it, my Mum had it and we were around her for hours but nothing happened to us. Well there is that chance that our immune system has dealt with Norovirus before or something of the like but I've never had an illness for less than 2 days...