I think the virus came in the ballast water from foriegn frieghters. It's a shame we can't agree on regulations to stop these introduced things gettig into the Lakes.
It can not survive like this so no Birds can not spread it. Birds would not even come into contact with it for all practical purposes. Movement of infected fish from one body to another is the main vector of it's spread.
VHS was originally a saltwater virus that has morphed into a freshwater one. It is presumed Cage farming trout and Salmon in Europe was the trigger for it to adapt to freshwater. The original vector into the great lakes for the virus is presumed to be ballast water or intentional release of infected fish. First year it hit we lost over 60% of the Musky on Lake St. Clair and in the Detroit river. It also wiped out hundreds of Drum and Round goby. (One of the few good things was seriously putting a dent in the round goby) Each year since it has caused mass mortality in one species or another.
This virus is no joke and is serious shibby. If you are in VHS infected waters do follow the laws put in place to slow this thing down. Drain your livewell and dump all buckets on shore. Destroy all leftover baitfish do not move them. sterilize your nets and equipment between watersheds. None of this is hard to do and if you value fishing or collecting you will be wise to do so.