I think it is meant be blood type O that is more susceptible to these viruses but honestly I don't think there is an awful lot in it. A is less likely and B is least likely. Obviously you can still get the virus but blood type B often is asymptomatic and A has less severe symptoms than O.

This is what I read on some academic article about norovirus and blood type that I found when i googled it after reading in a newspaper that blood type plays apart.
The article also said that more important is whether or not you are a secretor or non-secretor. I have no idea how you find out which you are but it said non-secretor is the one that means you are less likely to have symptoms but being a non-secretor is less common and makes you more susceptible to numerous more serious illnesses so I wouldn't go wishing I am one!

Personally i'm blood type A and I don't think I've ever had norovirus because I can't remember ever having d* or v* that lasted for more than 1 or 2 bouts. Last time I got sick I suppose it could have bee norovirus but I only had 1 bout of v* and nothing else.