Chickens diseases are a real and horrible thing. Years ago, we had a disease wipe us out and we had to cull everything that we owned and start over. Some diseases make the news. Some don’t. Some diseases are so easy to catch that a loose feather blowing around can spread it. Because of that, we keep a closed flock. No one is allowed in or out of our pens but us. We never meet at our home anymore and chose to meet at a gas station or church most of the time.
If your bird gets sick and dies, it is highly recommended to have it tested by a local poultry vet or the Arkansas State Veterinarian Lab. Right now, the state vet lab is free due to an umbrella grant (not sure when the grant ends so call first because it’s rather expensive).
The testing will take them from 2 days to 2 weeks and they will email you the results.
Here is an example of what they test for:
Little Rock Poultry 