I think you can have a necropsy done on one that's died. A few things I learned from our experience:
-Symptoms are described as "my chicken has a cold." But chickens don't get colds. They have wheezing, gasping, runny noses, and sometimes bubbles in the eyes. But often you can't even tell unless you're standing right beside them at night, when nothing else is moving, and you hear just a bit of whispering in their breath.
-If one got sick, they probably all got sick. Mine obviously did.
-It's the most contagious of all chicken diseases. Incubation is about 36 hours, and they get over it within a week, with a high survival rate.
-If they've survived, they're now immune to getting it again.
-Egg production will return, but it might not be the quality or quantity she had before. That's what I'm worried about for mine that got sick at 2 weeks old... I don't know if some of them will even lay, but I'm going to let them live until I find out. So you might just have to wait and see.
If it's been a month, and it was bronchitis, then it's come and gone. They can be carriers for the disease, though, and can infect future birds that have not had it yet. But if the rest of the flock has been with her, they've been exposed, so you don't need to do anything different. You can give her power-foods to help her recover, like cooking up some eggs and giving them to her. Or plain yogurt mixed with laying feed. They love that. I used yogurt as the recovery treatment for all of my birds, and they ate it UP!
