It has been some time since I studied Medical Microbiology, so someone with better knowledge please step in if I am wrong.
The flu virus is named based on two parts of its "body" the "H" part and the "N" part. I can not remember how many variations there are of each, but it is somewhere between 6-10 IIRC. That means you can have H1, H2, H3...combinded with N1, N2, N3 etc. When the virus is reproducing in its host, it can mutate. Let's say there are two different virus strains in a host. The host will be a pig. The pig has a flu virus, for arguments sake H3N5. This virus can jump from pig to human, as the two species are quite similar, genetically speaking. A bird comes in contact with the pig. It has the H1N5 virus. It infects the pig. Inside the pig, during replication, the H1 swaps with the pig's H3. Now you have an H1N5 virus that can be easily transmitted to humans. This is where the trouble would begin.
Remember that the influenza virus is a respitory disease, and the grouse is usually dead (not breathing) when you pick it up. Furthermore, while bird specific virus can make a species jump, for example to a pig, it can very rarely make a jump to humans.
I think that one should still use caution, but remember that just about 100% of the people who have died of this disease were farm workers who were in close contact with many live animals. The worry is that if it mutates (like in the pig example) in a manner that makes it jump easily into humans, we will be in trouble.
I'll find my text book later and add to this if someone so desires.