I just went through this just a few weeks ago. Unfortunatly, it does last quite a while. After the first few days of the virus, he should stop throwing up. Then, you are basically dealing with a LOT of dirty diapers. That part can last up to 2 weeks. We went through every bit of that 2 weeks! My doctor did recommend that I go to the pharmacey and get something called Lactinex. What that is are these packets of granules that you sprinkle in their food a few times a day and that is suppose to help the diapers to not be so runny. It worked for us once I got it. Once you start noticing the poop becoming harder, discontinue using it because it could have the opposite effect, such as constipation. This rotovirus is very contagious and you need to be careful after changing him to wipe down everything, otherwise it could last a lot longer and even worse, you could get it. Trust me, I did, and it was not fun. Be sure to clean you house throughly and take some clorox wipes and wipe down every toy, light switch, wipe container, door knob, ect. Good Luck!
P.S. _ You don't need a prescription for Lactinex but you do have to go up to the actual counter to get it.