It is something to worry about if ducks or geese fly anywhere near your place. The migratory routes do cross, which is how it got from one area of the country to Tennessee/Alabama now. Unfortunately, once those droppings hit the ground, other birds (any birds), insects, rodents, etc., that come into contact with the droppings can then track it into your coop or poultry yard. This is how it gets into those tightly controlled commercial poultry houses. Those places are intensely bio-secure in comparison to backyard flocks.
But for most of us, we simply can't keep to the insanely strict biosecurity measures the commercial poultry houses use. You can lock your flock down, do whatever you can to keep rodents and wild birds out, and keep the yard and coop unattractive for insects. Wear dedicated clothing and shoes into the yard and coop, and even wear disposable gloves and shoe covers. Use unactivated oxine to clean your coop and tools. Don't let anyone visit unless they do the same. No new birds in, no new birds out. But unless you are currently in a "hot spot" state, you are probably not going to resort to those measures and hope for the best.
Georgia just put a ban on all sales at flea markets, auctions, swaps, etc. because of the TN and AL outbreaks. Depending on who you talk to at the Ag Dept, they'll tell you it does not apply to individuals or it does apply, so conflicting information. Someone was told hatching eggs are in the ban, but that is ludicrous. AI is not passed through eggs to the chick.
I swear, sometimes, I think these outbreaks are just chances to stop backyard flocks altogether. They are saying you MUST be NPIP certified to sell anything and every bird tested and leg banded during this outbreak. Well, no stinking way I would ever be NPIP. It never means your flock is healthy, never. NPIP breeders are responsible for quite a few outbreaks themselves. Seems a way to get folks into that government program so they know who you are and what you have. Not this gal. If my birds are ill, I'll put them down. No government lackey is coming here to gas my flocks. But, thankfully, they haven't had anything contagious, nothing. Commercial flocks are more likely to come down ill than well-managed backyard flocks because of the crowded conditions.