What antibiotic helped her symptoms? Glad that she is better, but instead of colds, chickens get chronic respiratory diseases. Mycoplasma gallisepticum (MG) is common and coryza is another. Coryza smells bad, but testing would be needed to confirm which disease. Survivors are carriers for life. MG can also be passed through hatching eggs. The best thing is to close your flock and never rehome or sell birds until all are gone. You may never have another outbreak, but she or others could have an outbreak again.