Not an epidemic problem yet, but like the big one, it's coming.....
All we know is how bad they can be, they have been seen/identified in the Colorado River system (Lake Mead, Lake Havasu, etc).
Principal drinking water resevoir based lakes on, and those no where near or fed by the Colorado are nervous about what they can do once introduced. Those lakes and are taking novel means to protect the them from any introduction in the first place.
It's not like it's a widespred scourge, yet, but they're coming, big time, and the drinking water lakes and resevoirs are taking steps to protect their drinking water delivery (hardware) infrastructure, in some case by banning boating (a means that they 'could' be introduced.)
