The disease is acute to subacute at onset but progresses to a chronic state as the disease works through the flock. Common names for the disease are roup, cold and Coryza. Coryza is characterized by nasal discharge, facial swelling, sneezing, labored breathing and fetid odor of the exudates.
Coryza occurs worldwide.
In the United States, it is predominately found in small noncommercial, menagerie, or hobby type flocks. The causative agent is Hemophilus paragallinarum, a polar staining, pleomorphic, non-motile, gram negative rod that was first described in 1920. While chickens are the primary host of Coryza, pheasants, guinea fowl and turkeys are also susceptible. It is assumed that other gamebird species will become infected if commingle on a regular basis with chronically infected gamebirds or poultry flocks. The incubation period is 1 to 3 days and the course of the disease is 4 to 12 weeks.