Oh my goodness yes! My 3 year old just got over a terrible bug that lasted 6 days! It was awful I took him to the doctor twice over it because it got so bad! All you can do is wait it out and try and make them as comfortable as possible. Dehydration is the worst that can happen so make sure they are getting plenty of fluids and if they can't keep them down use electrolyte strips or something. Hope your little one gets better soon!